Cutis

Shampoo is a staple in hair grooming that is ever-evolving along with cultural trends. The global shampoo market is expected to reach an estimated value of $25.73 billion by 2019. A major driver of this upward trend in market growth is the increasing demand for natural and organic hair shampoos.¹ Society today has a growing fixation on healthy living practices, and as of late, the ingredients in shampoos and other cosmetic products have become one of the latest targets in the health-consciousness craze. In the age of the Internet where information—and misinformation—is widely accessible and dispersed, the general public often strives to self-educate on specialized matters that are out of their expertise. As a result, individuals have developed an aversion to using certain shampoos out of fear that the ingredients, often referred to as “chemicals” by patients due to their complex names, are unnatural and therefore unhealthy.^1,2 Product developers are working to meet the demand by reformulating shampoos with labels that indicate sulfate free or paraben free, despite the lack of proof that these formulations are an improvement over traditional approaches to hair health. Additionally, alternative methods of cleansing the hair and scalp, also known as the no-shampoo or “no-poo” method, have begun to gain popularity.^2,3

It is essential that dermatologists acknowledge the concerns that their patients have about common shampoo ingredients to dispel the myths that may misinform patient decision-making. This article reviews the controversy surrounding the use of sulfates and parabens in shampoos as well as commonly used shampoo alternatives. Due to the increased prevalence of dry hair shafts in the skin of color population, especially black women, this group is particularly interested in products that will minimize breakage and dryness of the hair. To that end, this population has great interest in the removal of chemical ingredients that may cause damage to the hair shafts, despite the lack of data to support sulfates and paraben damage to hair shafts or scalp skin. Blogs and uninformed hairstylists may propagate these beliefs in a group of consumers who are desperate for new approaches to hair fragility and breakage.

Surfactants and Sulfates

The cleansing ability of a shampoo depends on the surface activity of its detergents. Surface-active ingredients, or surfactants, reduce the surface tension between water and dirt, thus facilitating the removal of environmental dirt from the hair and scalp,⁴ which is achieved by a molecular structure containing both a hydrophilic and a lipophilic group. Sebum and dirt are bound by the lipophilic ends of the surfactant, becoming the center of a micelle structure with the hydrophilic molecule ends pointing outward. Dirt particles become water soluble and are removed from the scalp and hair shaft upon rinsing with water.⁴

Surfactants are classified according to the electric charge of the hydrophilic polar group as either anionic, cationic, amphoteric (zwitterionic), or nonionic.⁵ Each possesses different hair conditioning and cleansing qualities, and multiple surfactants are used in shampoos in differing ratios to accommodate different hair types. In most shampoos, the base consists of anionic and amphoteric surfactants. Depending on individual product requirements, nonionic and cationic surfactants are used to either modify the effects of the surfactants or as conditioning agents.^4,5

One subcategory of surfactants that receives much attention is the group of anionic surfactants known as sulfates. Sulfates, particularly sodium lauryl sulfate (SLS), recently have developed a negative reputation as cosmetic ingredients, as reports from various unscientific sources have labeled them as hazardous to one’s health; SLS has been described as a skin and scalp irritant, has been linked to cataract formation, and has even been wrongly labeled as carcinogenic.⁶ The origins of some of these claims are not clear, though they likely arose from the misinterpretation of complex scientific studies that are easily accessible to laypeople. The link between SLS and ocular irritation or cataract formation is a good illustration of this unsubstantiated fear. A study by Green et al⁷ showed that corneal exposure to extremely high concentrations of SLS following physical or chemical damage to the eye can result in a slowed healing process. The results of this study have since been wrongly quoted to state that SLS-containing products lead to blindness or severe corneal damage.⁸ A different study tested for possible ocular irritation in vivo by submerging the lens of an eye into a 20% SLS solution, which accurately approximates the concentration of SLS in rinse-off consumer products.⁹ However, to achieve ocular irritation, the eyes of laboratory animals were exposed to SLS constantly for 14 days, which would not occur in practical use.⁹ Similarly, a third study achieved cataract formation in a laboratory only by immersing the lens of an eye into a highly concentrated solution of SLS.¹⁰ Such studies are not appropriate representations of how SLS-containing products are used by consumers and have unfortunately been vulnerable to misinterpretation by the general public.

There is no known study that has shown SLS to be carcinogenic. One possible origin of this idea may be from the wrongful interpretation of studies that used SLS as a vehicle substance to test agents that were deemed to be carcinogenic.¹¹ Another possible source of the idea that SLS is carcinogenic comes from its association with 1,4-dioxane, a by-product of the synthesis of certain sulfates such as sodium laureth sulfate due to a process known as ethoxylation.^6,12 Although SLS does not undergo this process in its formation and is not linked to 1,4-dioxane, there is potential for cross-contamination of SLS with 1,4-dioxane, which cannot be overlooked. 1,4-Dioxane is classified as “possibly carcinogenic to humans (Group 2B)” by the International Agency for Research on Cancer,¹³ but screening of SLS for this substance prior to its use in commercial products is standard.

Sulfates are inexpensive detergents that are responsible for lather formation in shampoos as well as in many household cleaning agents.⁵ Sulfates, similar to all anionic surfactants, are characterized by a negatively charged hydrophilic polar group. The best-known and most commonly used anionic surfactants are sulfated fatty alcohols, alkyl sulfates, and their polyethoxylated analogues alkyl ether sulfates.^5,6 Sodium lauryl sulfate (also known as sodium laurilsulfate or sodium dodecyl sulfate) is the most common of them all, found in shampoo and conditioner formulations. Ammonium lauryl sulfate and sodium laureth sulfate are other sulfates commonly used in shampoos and household cleansing products. Sodium lauryl sulfate is a nonvolatile, water-soluble compound. Its partition coefficient (P₀), a measure of a substance’s hydrophilic or lipophilic nature, is low at 1.6, making it a rather hydrophilic substance.⁶ Hydrophilic substances tend to have low bioaccumulation profiles in the body. Additionally, SLS is readily biodegradable. It can be derived from both synthetic and naturally occurring sources; for example, palm kernel oil, petrolatum, and coconut oil are all sources of lauric acid, the starting ingredient used to synthesize SLS. Sodium lauryl sulfate is created by reacting lauryl alcohol with sulfur trioxide gas, followed by neutralization with sodium carbonate (also a naturally occurring compound).⁶ Sodium lauryl sulfate and other sulfate-containing shampoos widely replaced the usage of traditional soaps formulated from animal or vegetable fats, as these latter formations created a film of insoluble calcium salts on the hair strands upon contact with water, resulting in tangled, dull-appearing hair.⁵ Additionally, sulfates were preferred to the alkaline pH of traditional soap, which can be harsh on hair strands and cause irritation of the skin and mucous membranes.¹⁴ Because they are highly water soluble, sulfates enable the formulation of clear shampoos. They exhibit remarkable cleaning properties and lather formation.^5,14

Because sulfates are potent surfactants, they can remove dirt and debris as well as naturally produced healthy oils from the hair and scalp. As a result, sulfates can leave the hair feeling dry and stripped of moisture.^4,5 Sulfates are used as the primary detergents in the formulation of deep-cleaning shampoos, which are designed for people who accumulate a heavy buildup of dirt, sebum, and debris from frequent use of styling products. Due to their potent detergency, these shampoos typically are not used on a daily basis but rather at longer intervals.¹⁵ A downside to sulfates is that they can have cosmetically unpleasant properties, which can be compensated for by including appropriate softening additives in shampoo formulations.⁴ A number of anionic surfactants such as olefin sulfonate, alkyl sulfosuccinate, acyl peptides, and alkyl ether carboxylates are well tolerated by the skin and are used together with other anionic and amphoteric surfactants to optimize shampoo properties. Alternatively, sulfate-free shampoos are cleansers compounded by the removal of the anionic group and switched for surfactants with less detergency.^4,5

Preservatives and Parabens

Parabens refer to a group of esters of 4-hydroxybenzoic acid commonly used as preservatives in foods, pharmaceuticals, and cosmetics whose widespread use dates back to 1923.¹⁶ Concerns over the presence of parabens in shampoos and other cosmetics have been raised by patients for their reputed estrogenic and antiandrogenic effects and suspected involvement in carcinogenesis via endocrine modulation.^16,17 In in vitro studies done on yeast assays, parabens have shown weak estrogenic activity that increases in proportion to both the length and increased branching of the alkyl side chains in the paraben’s molecular structure.¹⁸ They are 10,000-fold less potent than 17β-estradiol. In in vivo animal studies, parabens show weak estrogenic activity and are 100,000-fold less potent than 17β-estradiol.¹⁸ 4-Hydroxybenzoic acid, a common metabolite, showed no estrogenic activity when tested both in vitro and in vivo.¹⁹ Some concerning research has implicated a link between parabens used in underarm cosmetics, such as deodorants and antiperspirants, and breast cancer¹⁶; however, the studies have been conflicting, and there is simply not enough data to assert that parabens cause breast cancer.

The Cosmetic Ingredient Review expert panel first reviewed parabens in 1984 and concluded that “methylparaben, ethylparaben, propylparaben, and butylparaben are safe as cosmetic ingredients in the present practices of use.”²⁰ They extended this statement to include isopropylparaben and isobutylparaben in a later review.²¹ In 2005, the Scientific Committee on Consumer Products (now known as the Scientific Committee for Consumer Safety) in Europe stated that methylparaben and ethylparaben can be used at levels up to 0.4% in products.²² This decision was reached due to reports of decreased sperm counts and testosterone levels in male juvenile rats exposed to these parabens; however, these reults were not successfully replicated in larger studies.^16,22 In 2010, the Scientific Committee for Consumer Safety revisited its stance on parabens, and they then revised their recommendations to say that concentrations of propylparaben and butylparaben should not exceed concentrations of 0.19%, based on “the conservative choice for the calculation of the [Margin-of-Safety] of butyl- and propylparaben.”²³ However, in 2011 the use of propylparaben and butylparaben was banned in Denmark for cosmetic products used in children 3 years or younger,¹⁶ and the European Commission subsequently amended their directive in 2014, banning isopropylparaben, isobutylparaben, phenylparaben, benzylparaben, and pentylparaben due to lack of data available to evaluate the human risk of these products.²⁴

Contrary to the trends in Europe, there currently are no regulations against the use of parabens in shampoos or other cosmetics in the United States. The American Cancer Society found that there is no evidence to suggest that the current levels of parabens in cosmetic products (eg, antiperspirants) increase one’s risk of breast cancer.²⁵ Parabens are readily absorbed into the body both transdermally and through ingestion but also are believed to be rapidly transformed into harmless and nonspecific metabolites; they are readily metabolized by the liver and excreted in urine, and there is no measured accumulation in tissues.¹⁷

Parabens continue to be the most widely used preservatives in personal care products, usually in conjunction with other preservatives. Parabens are good biocides; short-chain esters (eg, methylparabens, ethylparabens) are effective against gram-positive bacteria and are weakly effective against gram-negative bacteria. Long-chain paraben esters (eg, propylparabens, butylparabens) are effective against mold and yeast. The addition of other preservatives creates a broad spectrum of antimicrobial defense in consumer products. Other preservatives include formaldehyde releasers or phenoxyethanol, as well as chelating agents such as EDTA, which improve the stability of these cosmetic products when exposed to air.¹⁶ Parabens are naturally occurring substances found in foods such as blueberries, barley, strawberries, yeast, olives, and grapes. As a colorless, odorless, and inexpensive substance, their use has been heavily favored in cosmetic and food products.¹⁶

Shampoo Alternatives and the No-Poo Method

Although research has not demonstrated any long-term danger to using shampoo, certain chemicals found in shampoos have the potential to irritate the scalp. Commonly cited allergens in shampoos include cocamidopropyl betaine, propylene glycol, vitamin E (tocopherol), parabens, and benzophenones.⁵ Additionally, the rising use of formaldehyde-releasing preservatives and isothiazolinones due to mounting pressures to move away from parabens has led to an increase in cases of allergic contact dermatitis (ACD).¹⁶ However, the irritability (rather than allergenicity) of these substances often is established during patch testing, a method of detecting delayed-type allergic reactions, which is important to note because patch testing requires a substance to be exposed to the skin for 24 to 48 hours, whereas exposure to shampoo ingredients may last a matter of minutes at most and occur in lesser concentrations because the ingredients are diluted by water in the rinsing process. Given these differences, it is unlikely that a patient would develop a true allergic response from regular shampoo use. Nevertheless, in patients who are already sensitized, exposure could conceivably trigger ACD, and patients must be cognizant of the composition of their shampoos.¹⁶

The no-poo method refers to the avoidance of commercial shampoo products when cleansing the hair and scalp and encompasses different methods of cleansing the hair, such as the use of household items (eg, baking soda, apple cider vinegar [ACV]), the use of conditioners to wash the hair (also known as conditioner-only washing or co-washing), treating the scalp with tea tree oil, or simply rinsing the hair with water. Proponents of the no-poo method believe that abstaining from shampoo use leads to healthier hair, retained natural oils, and less exposure to supposedly dangerous chemicals such as parabens or sulfates.^2,3,26-28 However, there are no known studies in the literature that assess or support the hypotheses of the no-poo method.

Baking Soda and ACV
Baking soda (sodium bicarbonate) is a substance commonly found in the average household. It has been used in toothpaste formulas and cosmetic products and is known for its acid-neutralizing properties. Baking soda has been shown to have some antifungal and viricidal properties through an unknown mechanism of action.²⁸ It has gained popularity for its use as a means of reducing the appearance of excessive greasiness of the hair shafts. Users also have reported that when washing their hair with baking soda, they are able to achieve a clean scalp and hair that feels soft to the touch.^2,3,26,27,29 Despite these reports, users must beware of using baking soda without adequately diluting it with water. Baking soda is a known alkaline irritant.^26,30 With a pH of 9, baking soda causes the cuticle layer of the hair fiber to open, increasing the capacity for water absorption. Water penetrates the scales that open, breaking the hydrogen bonds of the keratin molecule.³¹ Keratin is a spiral helical molecule that keeps its shape due to hydrogen, disulfide, and ionic bonds, as well as Van der Waals force.³⁰ Hydrolysis of these bonds due to exposure to baking soda lowers the elasticity of the hair and increases the negative electrical net charge of the hair fiber surface, which leads to increased friction between fibers, cuticle damage, hair fragility, and fiber breakage.^32,33

Apple cider vinegar is an apple-derived acetic acid solution with a pH ranging from 3.1 to 5.²⁸ The pH range of ACV is considered to be ideal for hair by no-poo proponents, as it is similar to the natural pH of the scalp. Its acidic properties are responsible for its antimicrobial abilities, particularly its effectiveness against gram-negative bacteria.³⁰ The acetic acid of ACV can partially interrupt oil interfaces, which contributes to its mild ability to remove product residue and scalp buildup from the hair shaft; the acetic acid also tightens the cuticles on hair fibers.³³ Apple cider vinegar is used as a means of cleansing the hair and scalp by no-poo proponents^2,3,26; other uses for ACV include using it as a rinse following washing and/or conditioning of the hair or as a means of preserving color in color-treated hair. There also is evidence that ACV may have antifungal properties.²⁸ However, consumers must be aware that if it is not diluted in water, ACV may be too caustic for direct application to the hair and may lead to damage; it can be irritating to eyes, mucus membranes, and acutely inflamed skin. Also, vinegar rinses used on processed or chemically damaged hair may lead to increased hair fragility.^2,3

Hair fibers have a pH of 3.67, while the scalp has a pH between 4.5 and 6.2. This slightly acidic film acts as a barrier to viruses, bacteria, and other potential contaminants.³³ Studies have shown that the pH of skin increases in proportion to the pH of the cleanser used.³⁴ Therefore, due to the naturally acidic pH of the scalp, acid-balanced shampoos generally are recommended. Shampoos should not have a pH higher than 5.5, as hair shafts can swell due to alkalinization, which can be prevented by pH balancing the shampoo through the addition of an acidic substance (eg, glycolic acid, citric acid) to lower the pH down to approximately 5.5. Apple cider vinegar often is used for this purpose. However, one study revealed that 82% of shampoos already have an acidic pH.³⁴

Conditioner-Only Washing (Co-washing)
Conditioner-only washing, or co-washing, is a widely practiced method of hair grooming. It is popular among individuals who find that commercial shampoos strip too much of the natural hair oils away, leaving the hair rough or unmanageable. Co-washing is not harmful to the hair; however, the molecular structure and function of a conditioner and that of a shampoo are very different.^5,35,36 Conditioners are not formulated to remove dirt and buildup in the hair but rather to add substances to the hair, and thus cannot provide extensive cleansing of the hair and scalp; therefore, it is inappropriate to use co-washing as a replacement for shampooing. Quaternary conditioning agents are an exception because they contain amphoteric detergents comprised of both anionic and cationic groups, which allow them both the ability to remove dirt and sebum with its anionic group, typically found in shampoos, as well as the ability to coat and condition the hair due to the high affinity of the cationic group for the negatively charged hair fibers.^36,37 Amphoteric detergents are commonly found in 2-in-1 conditioning cleansers, among other ingredients, such as hydrolyzed animal proteins that temporarily plug surface defects on the hair fiber, and dimethicone, a synthetic oil that creates a thin film over the hair shaft, increasing shine and manageability. Of note, these conditioning shampoos are ideal for individuals with minimal product buildup on the hair and scalp and are not adequate scalp cleansers for individuals who either wash their hair infrequently or who regularly use hairstyling products.^36,37

Tea Tree Oil
Tea tree oil is an essential oil extracted from the Melaleuca alternifolia plant of the Myrtaceae family. It is native to the coast of northeastern Australia. A holy grail of natural cosmetics, tea tree oil is widely known for its antiviral, antifungal, and antiseptic properties.³⁸ Although not used as a stand-alone cleanser, it is often added to a number of cosmetic products, including shampoos and co-washes. Although deemed safe for topical use, it has been shown to be quite toxic when ingested. Symptoms of ingestion include nausea, vomiting, hallucinations, and coma. The common concern with tea tree oil is its ability to cause ACD. In particular, it is believed that the oxidation products of tea tree oil are allergenic rather than the tea tree oil itself. The evaluation of tea tree oil as a potential contact allergen has been quite difficult; it consists of more than 100 distinct compounds and is often mislabeled, or does not meet the guidelines of the International Organization for Standardization. Nonetheless, the prevalence of ACD due to tea tree oil is low (approximately 1.4%). Despite its low prevalence, tea tree oil should remain in the differential as an ACD-inducing agent. Patch testing with the patient’s supply of tea tree oil is advised when possible.³⁸

Conclusion

It is customary that the ingredients used in shampoos undergo periodic testing and monitoring to assure the safety of their use. Although it is encouraging that patients are proactive in their efforts to stay abreast of the literature, it is still important that cosmetic scientists, dermatologists, and other experts remain at the forefront of educating the public about these substances. Not doing so can result in the propagation of misinformation and unnecessary fears, which can lead to the adaptation of unhygienic or even unsafe hair care practices. As dermatologists, we must ensure that patients are educated about the benefits and hazards of off-label use of household ingredients to the extent that evidence-based medicine permits. Patients must be informed that not all synthetic substances are harmful, and likewise not all naturally occurring substances are safe.

Shampoo is a staple in hair grooming that is ever-evolving along with cultural trends. The global shampoo market is expected to reach an estimated value of $25.73 billion by 2019. A major driver of this upward trend in market growth is the increasing demand for natural and organic hair shampoos.¹ Society today has a growing fixation on healthy living practices, and as of late, the ingredients in shampoos and other cosmetic products have become one of the latest targets in the health-consciousness craze. In the age of the Internet where information—and misinformation—is widely accessible and dispersed, the general public often strives to self-educate on specialized matters that are out of their expertise. As a result, individuals have developed an aversion to using certain shampoos out of fear that the ingredients, often referred to as “chemicals” by patients due to their complex names, are unnatural and therefore unhealthy.^1,2 Product developers are working to meet the demand by reformulating shampoos with labels that indicate sulfate free or paraben free, despite the lack of proof that these formulations are an improvement over traditional approaches to hair health. Additionally, alternative methods of cleansing the hair and scalp, also known as the no-shampoo or “no-poo” method, have begun to gain popularity.^2,3

It is essential that dermatologists acknowledge the concerns that their patients have about common shampoo ingredients to dispel the myths that may misinform patient decision-making. This article reviews the controversy surrounding the use of sulfates and parabens in shampoos as well as commonly used shampoo alternatives. Due to the increased prevalence of dry hair shafts in the skin of color population, especially black women, this group is particularly interested in products that will minimize breakage and dryness of the hair. To that end, this population has great interest in the removal of chemical ingredients that may cause damage to the hair shafts, despite the lack of data to support sulfates and paraben damage to hair shafts or scalp skin. Blogs and uninformed hairstylists may propagate these beliefs in a group of consumers who are desperate for new approaches to hair fragility and breakage.

Surfactants and Sulfates

The cleansing ability of a shampoo depends on the surface activity of its detergents. Surface-active ingredients, or surfactants, reduce the surface tension between water and dirt, thus facilitating the removal of environmental dirt from the hair and scalp,⁴ which is achieved by a molecular structure containing both a hydrophilic and a lipophilic group. Sebum and dirt are bound by the lipophilic ends of the surfactant, becoming the center of a micelle structure with the hydrophilic molecule ends pointing outward. Dirt particles become water soluble and are removed from the scalp and hair shaft upon rinsing with water.⁴

Surfactants are classified according to the electric charge of the hydrophilic polar group as either anionic, cationic, amphoteric (zwitterionic), or nonionic.⁵ Each possesses different hair conditioning and cleansing qualities, and multiple surfactants are used in shampoos in differing ratios to accommodate different hair types. In most shampoos, the base consists of anionic and amphoteric surfactants. Depending on individual product requirements, nonionic and cationic surfactants are used to either modify the effects of the surfactants or as conditioning agents.^4,5

One subcategory of surfactants that receives much attention is the group of anionic surfactants known as sulfates. Sulfates, particularly sodium lauryl sulfate (SLS), recently have developed a negative reputation as cosmetic ingredients, as reports from various unscientific sources have labeled them as hazardous to one’s health; SLS has been described as a skin and scalp irritant, has been linked to cataract formation, and has even been wrongly labeled as carcinogenic.⁶ The origins of some of these claims are not clear, though they likely arose from the misinterpretation of complex scientific studies that are easily accessible to laypeople. The link between SLS and ocular irritation or cataract formation is a good illustration of this unsubstantiated fear. A study by Green et al⁷ showed that corneal exposure to extremely high concentrations of SLS following physical or chemical damage to the eye can result in a slowed healing process. The results of this study have since been wrongly quoted to state that SLS-containing products lead to blindness or severe corneal damage.⁸ A different study tested for possible ocular irritation in vivo by submerging the lens of an eye into a 20% SLS solution, which accurately approximates the concentration of SLS in rinse-off consumer products.⁹ However, to achieve ocular irritation, the eyes of laboratory animals were exposed to SLS constantly for 14 days, which would not occur in practical use.⁹ Similarly, a third study achieved cataract formation in a laboratory only by immersing the lens of an eye into a highly concentrated solution of SLS.¹⁰ Such studies are not appropriate representations of how SLS-containing products are used by consumers and have unfortunately been vulnerable to misinterpretation by the general public.

There is no known study that has shown SLS to be carcinogenic. One possible origin of this idea may be from the wrongful interpretation of studies that used SLS as a vehicle substance to test agents that were deemed to be carcinogenic.¹¹ Another possible source of the idea that SLS is carcinogenic comes from its association with 1,4-dioxane, a by-product of the synthesis of certain sulfates such as sodium laureth sulfate due to a process known as ethoxylation.^6,12 Although SLS does not undergo this process in its formation and is not linked to 1,4-dioxane, there is potential for cross-contamination of SLS with 1,4-dioxane, which cannot be overlooked. 1,4-Dioxane is classified as “possibly carcinogenic to humans (Group 2B)” by the International Agency for Research on Cancer,¹³ but screening of SLS for this substance prior to its use in commercial products is standard.

Sulfates are inexpensive detergents that are responsible for lather formation in shampoos as well as in many household cleaning agents.⁵ Sulfates, similar to all anionic surfactants, are characterized by a negatively charged hydrophilic polar group. The best-known and most commonly used anionic surfactants are sulfated fatty alcohols, alkyl sulfates, and their polyethoxylated analogues alkyl ether sulfates.^5,6 Sodium lauryl sulfate (also known as sodium laurilsulfate or sodium dodecyl sulfate) is the most common of them all, found in shampoo and conditioner formulations. Ammonium lauryl sulfate and sodium laureth sulfate are other sulfates commonly used in shampoos and household cleansing products. Sodium lauryl sulfate is a nonvolatile, water-soluble compound. Its partition coefficient (P₀), a measure of a substance’s hydrophilic or lipophilic nature, is low at 1.6, making it a rather hydrophilic substance.⁶ Hydrophilic substances tend to have low bioaccumulation profiles in the body. Additionally, SLS is readily biodegradable. It can be derived from both synthetic and naturally occurring sources; for example, palm kernel oil, petrolatum, and coconut oil are all sources of lauric acid, the starting ingredient used to synthesize SLS. Sodium lauryl sulfate is created by reacting lauryl alcohol with sulfur trioxide gas, followed by neutralization with sodium carbonate (also a naturally occurring compound).⁶ Sodium lauryl sulfate and other sulfate-containing shampoos widely replaced the usage of traditional soaps formulated from animal or vegetable fats, as these latter formations created a film of insoluble calcium salts on the hair strands upon contact with water, resulting in tangled, dull-appearing hair.⁵ Additionally, sulfates were preferred to the alkaline pH of traditional soap, which can be harsh on hair strands and cause irritation of the skin and mucous membranes.¹⁴ Because they are highly water soluble, sulfates enable the formulation of clear shampoos. They exhibit remarkable cleaning properties and lather formation.^5,14

Because sulfates are potent surfactants, they can remove dirt and debris as well as naturally produced healthy oils from the hair and scalp. As a result, sulfates can leave the hair feeling dry and stripped of moisture.^4,5 Sulfates are used as the primary detergents in the formulation of deep-cleaning shampoos, which are designed for people who accumulate a heavy buildup of dirt, sebum, and debris from frequent use of styling products. Due to their potent detergency, these shampoos typically are not used on a daily basis but rather at longer intervals.¹⁵ A downside to sulfates is that they can have cosmetically unpleasant properties, which can be compensated for by including appropriate softening additives in shampoo formulations.⁴ A number of anionic surfactants such as olefin sulfonate, alkyl sulfosuccinate, acyl peptides, and alkyl ether carboxylates are well tolerated by the skin and are used together with other anionic and amphoteric surfactants to optimize shampoo properties. Alternatively, sulfate-free shampoos are cleansers compounded by the removal of the anionic group and switched for surfactants with less detergency.^4,5

Preservatives and Parabens

Parabens refer to a group of esters of 4-hydroxybenzoic acid commonly used as preservatives in foods, pharmaceuticals, and cosmetics whose widespread use dates back to 1923.¹⁶ Concerns over the presence of parabens in shampoos and other cosmetics have been raised by patients for their reputed estrogenic and antiandrogenic effects and suspected involvement in carcinogenesis via endocrine modulation.^16,17 In in vitro studies done on yeast assays, parabens have shown weak estrogenic activity that increases in proportion to both the length and increased branching of the alkyl side chains in the paraben’s molecular structure.¹⁸ They are 10,000-fold less potent than 17β-estradiol. In in vivo animal studies, parabens show weak estrogenic activity and are 100,000-fold less potent than 17β-estradiol.¹⁸ 4-Hydroxybenzoic acid, a common metabolite, showed no estrogenic activity when tested both in vitro and in vivo.¹⁹ Some concerning research has implicated a link between parabens used in underarm cosmetics, such as deodorants and antiperspirants, and breast cancer¹⁶; however, the studies have been conflicting, and there is simply not enough data to assert that parabens cause breast cancer.

The Cosmetic Ingredient Review expert panel first reviewed parabens in 1984 and concluded that “methylparaben, ethylparaben, propylparaben, and butylparaben are safe as cosmetic ingredients in the present practices of use.”²⁰ They extended this statement to include isopropylparaben and isobutylparaben in a later review.²¹ In 2005, the Scientific Committee on Consumer Products (now known as the Scientific Committee for Consumer Safety) in Europe stated that methylparaben and ethylparaben can be used at levels up to 0.4% in products.²² This decision was reached due to reports of decreased sperm counts and testosterone levels in male juvenile rats exposed to these parabens; however, these reults were not successfully replicated in larger studies.^16,22 In 2010, the Scientific Committee for Consumer Safety revisited its stance on parabens, and they then revised their recommendations to say that concentrations of propylparaben and butylparaben should not exceed concentrations of 0.19%, based on “the conservative choice for the calculation of the [Margin-of-Safety] of butyl- and propylparaben.”²³ However, in 2011 the use of propylparaben and butylparaben was banned in Denmark for cosmetic products used in children 3 years or younger,¹⁶ and the European Commission subsequently amended their directive in 2014, banning isopropylparaben, isobutylparaben, phenylparaben, benzylparaben, and pentylparaben due to lack of data available to evaluate the human risk of these products.²⁴

Contrary to the trends in Europe, there currently are no regulations against the use of parabens in shampoos or other cosmetics in the United States. The American Cancer Society found that there is no evidence to suggest that the current levels of parabens in cosmetic products (eg, antiperspirants) increase one’s risk of breast cancer.²⁵ Parabens are readily absorbed into the body both transdermally and through ingestion but also are believed to be rapidly transformed into harmless and nonspecific metabolites; they are readily metabolized by the liver and excreted in urine, and there is no measured accumulation in tissues.¹⁷

Parabens continue to be the most widely used preservatives in personal care products, usually in conjunction with other preservatives. Parabens are good biocides; short-chain esters (eg, methylparabens, ethylparabens) are effective against gram-positive bacteria and are weakly effective against gram-negative bacteria. Long-chain paraben esters (eg, propylparabens, butylparabens) are effective against mold and yeast. The addition of other preservatives creates a broad spectrum of antimicrobial defense in consumer products. Other preservatives include formaldehyde releasers or phenoxyethanol, as well as chelating agents such as EDTA, which improve the stability of these cosmetic products when exposed to air.¹⁶ Parabens are naturally occurring substances found in foods such as blueberries, barley, strawberries, yeast, olives, and grapes. As a colorless, odorless, and inexpensive substance, their use has been heavily favored in cosmetic and food products.¹⁶

Shampoo Alternatives and the No-Poo Method

Although research has not demonstrated any long-term danger to using shampoo, certain chemicals found in shampoos have the potential to irritate the scalp. Commonly cited allergens in shampoos include cocamidopropyl betaine, propylene glycol, vitamin E (tocopherol), parabens, and benzophenones.⁵ Additionally, the rising use of formaldehyde-releasing preservatives and isothiazolinones due to mounting pressures to move away from parabens has led to an increase in cases of allergic contact dermatitis (ACD).¹⁶ However, the irritability (rather than allergenicity) of these substances often is established during patch testing, a method of detecting delayed-type allergic reactions, which is important to note because patch testing requires a substance to be exposed to the skin for 24 to 48 hours, whereas exposure to shampoo ingredients may last a matter of minutes at most and occur in lesser concentrations because the ingredients are diluted by water in the rinsing process. Given these differences, it is unlikely that a patient would develop a true allergic response from regular shampoo use. Nevertheless, in patients who are already sensitized, exposure could conceivably trigger ACD, and patients must be cognizant of the composition of their shampoos.¹⁶

The no-poo method refers to the avoidance of commercial shampoo products when cleansing the hair and scalp and encompasses different methods of cleansing the hair, such as the use of household items (eg, baking soda, apple cider vinegar [ACV]), the use of conditioners to wash the hair (also known as conditioner-only washing or co-washing), treating the scalp with tea tree oil, or simply rinsing the hair with water. Proponents of the no-poo method believe that abstaining from shampoo use leads to healthier hair, retained natural oils, and less exposure to supposedly dangerous chemicals such as parabens or sulfates.^2,3,26-28 However, there are no known studies in the literature that assess or support the hypotheses of the no-poo method.

Baking Soda and ACV
Baking soda (sodium bicarbonate) is a substance commonly found in the average household. It has been used in toothpaste formulas and cosmetic products and is known for its acid-neutralizing properties. Baking soda has been shown to have some antifungal and viricidal properties through an unknown mechanism of action.²⁸ It has gained popularity for its use as a means of reducing the appearance of excessive greasiness of the hair shafts. Users also have reported that when washing their hair with baking soda, they are able to achieve a clean scalp and hair that feels soft to the touch.^2,3,26,27,29 Despite these reports, users must beware of using baking soda without adequately diluting it with water. Baking soda is a known alkaline irritant.^26,30 With a pH of 9, baking soda causes the cuticle layer of the hair fiber to open, increasing the capacity for water absorption. Water penetrates the scales that open, breaking the hydrogen bonds of the keratin molecule.³¹ Keratin is a spiral helical molecule that keeps its shape due to hydrogen, disulfide, and ionic bonds, as well as Van der Waals force.³⁰ Hydrolysis of these bonds due to exposure to baking soda lowers the elasticity of the hair and increases the negative electrical net charge of the hair fiber surface, which leads to increased friction between fibers, cuticle damage, hair fragility, and fiber breakage.^32,33

Apple cider vinegar is an apple-derived acetic acid solution with a pH ranging from 3.1 to 5.²⁸ The pH range of ACV is considered to be ideal for hair by no-poo proponents, as it is similar to the natural pH of the scalp. Its acidic properties are responsible for its antimicrobial abilities, particularly its effectiveness against gram-negative bacteria.³⁰ The acetic acid of ACV can partially interrupt oil interfaces, which contributes to its mild ability to remove product residue and scalp buildup from the hair shaft; the acetic acid also tightens the cuticles on hair fibers.³³ Apple cider vinegar is used as a means of cleansing the hair and scalp by no-poo proponents^2,3,26; other uses for ACV include using it as a rinse following washing and/or conditioning of the hair or as a means of preserving color in color-treated hair. There also is evidence that ACV may have antifungal properties.²⁸ However, consumers must be aware that if it is not diluted in water, ACV may be too caustic for direct application to the hair and may lead to damage; it can be irritating to eyes, mucus membranes, and acutely inflamed skin. Also, vinegar rinses used on processed or chemically damaged hair may lead to increased hair fragility.^2,3

Hair fibers have a pH of 3.67, while the scalp has a pH between 4.5 and 6.2. This slightly acidic film acts as a barrier to viruses, bacteria, and other potential contaminants.³³ Studies have shown that the pH of skin increases in proportion to the pH of the cleanser used.³⁴ Therefore, due to the naturally acidic pH of the scalp, acid-balanced shampoos generally are recommended. Shampoos should not have a pH higher than 5.5, as hair shafts can swell due to alkalinization, which can be prevented by pH balancing the shampoo through the addition of an acidic substance (eg, glycolic acid, citric acid) to lower the pH down to approximately 5.5. Apple cider vinegar often is used for this purpose. However, one study revealed that 82% of shampoos already have an acidic pH.³⁴

Conditioner-Only Washing (Co-washing)
Conditioner-only washing, or co-washing, is a widely practiced method of hair grooming. It is popular among individuals who find that commercial shampoos strip too much of the natural hair oils away, leaving the hair rough or unmanageable. Co-washing is not harmful to the hair; however, the molecular structure and function of a conditioner and that of a shampoo are very different.^5,35,36 Conditioners are not formulated to remove dirt and buildup in the hair but rather to add substances to the hair, and thus cannot provide extensive cleansing of the hair and scalp; therefore, it is inappropriate to use co-washing as a replacement for shampooing. Quaternary conditioning agents are an exception because they contain amphoteric detergents comprised of both anionic and cationic groups, which allow them both the ability to remove dirt and sebum with its anionic group, typically found in shampoos, as well as the ability to coat and condition the hair due to the high affinity of the cationic group for the negatively charged hair fibers.^36,37 Amphoteric detergents are commonly found in 2-in-1 conditioning cleansers, among other ingredients, such as hydrolyzed animal proteins that temporarily plug surface defects on the hair fiber, and dimethicone, a synthetic oil that creates a thin film over the hair shaft, increasing shine and manageability. Of note, these conditioning shampoos are ideal for individuals with minimal product buildup on the hair and scalp and are not adequate scalp cleansers for individuals who either wash their hair infrequently or who regularly use hairstyling products.^36,37

Tea Tree Oil
Tea tree oil is an essential oil extracted from the Melaleuca alternifolia plant of the Myrtaceae family. It is native to the coast of northeastern Australia. A holy grail of natural cosmetics, tea tree oil is widely known for its antiviral, antifungal, and antiseptic properties.³⁸ Although not used as a stand-alone cleanser, it is often added to a number of cosmetic products, including shampoos and co-washes. Although deemed safe for topical use, it has been shown to be quite toxic when ingested. Symptoms of ingestion include nausea, vomiting, hallucinations, and coma. The common concern with tea tree oil is its ability to cause ACD. In particular, it is believed that the oxidation products of tea tree oil are allergenic rather than the tea tree oil itself. The evaluation of tea tree oil as a potential contact allergen has been quite difficult; it consists of more than 100 distinct compounds and is often mislabeled, or does not meet the guidelines of the International Organization for Standardization. Nonetheless, the prevalence of ACD due to tea tree oil is low (approximately 1.4%). Despite its low prevalence, tea tree oil should remain in the differential as an ACD-inducing agent. Patch testing with the patient’s supply of tea tree oil is advised when possible.³⁸

Conclusion

It is customary that the ingredients used in shampoos undergo periodic testing and monitoring to assure the safety of their use. Although it is encouraging that patients are proactive in their efforts to stay abreast of the literature, it is still important that cosmetic scientists, dermatologists, and other experts remain at the forefront of educating the public about these substances. Not doing so can result in the propagation of misinformation and unnecessary fears, which can lead to the adaptation of unhygienic or even unsafe hair care practices. As dermatologists, we must ensure that patients are educated about the benefits and hazards of off-label use of household ingredients to the extent that evidence-based medicine permits. Patients must be informed that not all synthetic substances are harmful, and likewise not all naturally occurring substances are safe.

Shampoo is a staple in hair grooming that is ever-evolving along with cultural trends. The global shampoo market is expected to reach an estimated value of $25.73 billion by 2019. A major driver of this upward trend in market growth is the increasing demand for natural and organic hair shampoos.¹ Society today has a growing fixation on healthy living practices, and as of late, the ingredients in shampoos and other cosmetic products have become one of the latest targets in the health-consciousness craze. In the age of the Internet where information—and misinformation—is widely accessible and dispersed, the general public often strives to self-educate on specialized matters that are out of their expertise. As a result, individuals have developed an aversion to using certain shampoos out of fear that the ingredients, often referred to as “chemicals” by patients due to their complex names, are unnatural and therefore unhealthy.^1,2 Product developers are working to meet the demand by reformulating shampoos with labels that indicate sulfate free or paraben free, despite the lack of proof that these formulations are an improvement over traditional approaches to hair health. Additionally, alternative methods of cleansing the hair and scalp, also known as the no-shampoo or “no-poo” method, have begun to gain popularity.^2,3

It is essential that dermatologists acknowledge the concerns that their patients have about common shampoo ingredients to dispel the myths that may misinform patient decision-making. This article reviews the controversy surrounding the use of sulfates and parabens in shampoos as well as commonly used shampoo alternatives. Due to the increased prevalence of dry hair shafts in the skin of color population, especially black women, this group is particularly interested in products that will minimize breakage and dryness of the hair. To that end, this population has great interest in the removal of chemical ingredients that may cause damage to the hair shafts, despite the lack of data to support sulfates and paraben damage to hair shafts or scalp skin. Blogs and uninformed hairstylists may propagate these beliefs in a group of consumers who are desperate for new approaches to hair fragility and breakage.

Surfactants and Sulfates

The cleansing ability of a shampoo depends on the surface activity of its detergents. Surface-active ingredients, or surfactants, reduce the surface tension between water and dirt, thus facilitating the removal of environmental dirt from the hair and scalp,⁴ which is achieved by a molecular structure containing both a hydrophilic and a lipophilic group. Sebum and dirt are bound by the lipophilic ends of the surfactant, becoming the center of a micelle structure with the hydrophilic molecule ends pointing outward. Dirt particles become water soluble and are removed from the scalp and hair shaft upon rinsing with water.⁴

Surfactants are classified according to the electric charge of the hydrophilic polar group as either anionic, cationic, amphoteric (zwitterionic), or nonionic.⁵ Each possesses different hair conditioning and cleansing qualities, and multiple surfactants are used in shampoos in differing ratios to accommodate different hair types. In most shampoos, the base consists of anionic and amphoteric surfactants. Depending on individual product requirements, nonionic and cationic surfactants are used to either modify the effects of the surfactants or as conditioning agents.^4,5

One subcategory of surfactants that receives much attention is the group of anionic surfactants known as sulfates. Sulfates, particularly sodium lauryl sulfate (SLS), recently have developed a negative reputation as cosmetic ingredients, as reports from various unscientific sources have labeled them as hazardous to one’s health; SLS has been described as a skin and scalp irritant, has been linked to cataract formation, and has even been wrongly labeled as carcinogenic.⁶ The origins of some of these claims are not clear, though they likely arose from the misinterpretation of complex scientific studies that are easily accessible to laypeople. The link between SLS and ocular irritation or cataract formation is a good illustration of this unsubstantiated fear. A study by Green et al⁷ showed that corneal exposure to extremely high concentrations of SLS following physical or chemical damage to the eye can result in a slowed healing process. The results of this study have since been wrongly quoted to state that SLS-containing products lead to blindness or severe corneal damage.⁸ A different study tested for possible ocular irritation in vivo by submerging the lens of an eye into a 20% SLS solution, which accurately approximates the concentration of SLS in rinse-off consumer products.⁹ However, to achieve ocular irritation, the eyes of laboratory animals were exposed to SLS constantly for 14 days, which would not occur in practical use.⁹ Similarly, a third study achieved cataract formation in a laboratory only by immersing the lens of an eye into a highly concentrated solution of SLS.¹⁰ Such studies are not appropriate representations of how SLS-containing products are used by consumers and have unfortunately been vulnerable to misinterpretation by the general public.

There is no known study that has shown SLS to be carcinogenic. One possible origin of this idea may be from the wrongful interpretation of studies that used SLS as a vehicle substance to test agents that were deemed to be carcinogenic.¹¹ Another possible source of the idea that SLS is carcinogenic comes from its association with 1,4-dioxane, a by-product of the synthesis of certain sulfates such as sodium laureth sulfate due to a process known as ethoxylation.^6,12 Although SLS does not undergo this process in its formation and is not linked to 1,4-dioxane, there is potential for cross-contamination of SLS with 1,4-dioxane, which cannot be overlooked. 1,4-Dioxane is classified as “possibly carcinogenic to humans (Group 2B)” by the International Agency for Research on Cancer,¹³ but screening of SLS for this substance prior to its use in commercial products is standard.

Sulfates are inexpensive detergents that are responsible for lather formation in shampoos as well as in many household cleaning agents.⁵ Sulfates, similar to all anionic surfactants, are characterized by a negatively charged hydrophilic polar group. The best-known and most commonly used anionic surfactants are sulfated fatty alcohols, alkyl sulfates, and their polyethoxylated analogues alkyl ether sulfates.^5,6 Sodium lauryl sulfate (also known as sodium laurilsulfate or sodium dodecyl sulfate) is the most common of them all, found in shampoo and conditioner formulations. Ammonium lauryl sulfate and sodium laureth sulfate are other sulfates commonly used in shampoos and household cleansing products. Sodium lauryl sulfate is a nonvolatile, water-soluble compound. Its partition coefficient (P₀), a measure of a substance’s hydrophilic or lipophilic nature, is low at 1.6, making it a rather hydrophilic substance.⁶ Hydrophilic substances tend to have low bioaccumulation profiles in the body. Additionally, SLS is readily biodegradable. It can be derived from both synthetic and naturally occurring sources; for example, palm kernel oil, petrolatum, and coconut oil are all sources of lauric acid, the starting ingredient used to synthesize SLS. Sodium lauryl sulfate is created by reacting lauryl alcohol with sulfur trioxide gas, followed by neutralization with sodium carbonate (also a naturally occurring compound).⁶ Sodium lauryl sulfate and other sulfate-containing shampoos widely replaced the usage of traditional soaps formulated from animal or vegetable fats, as these latter formations created a film of insoluble calcium salts on the hair strands upon contact with water, resulting in tangled, dull-appearing hair.⁵ Additionally, sulfates were preferred to the alkaline pH of traditional soap, which can be harsh on hair strands and cause irritation of the skin and mucous membranes.¹⁴ Because they are highly water soluble, sulfates enable the formulation of clear shampoos. They exhibit remarkable cleaning properties and lather formation.^5,14

Because sulfates are potent surfactants, they can remove dirt and debris as well as naturally produced healthy oils from the hair and scalp. As a result, sulfates can leave the hair feeling dry and stripped of moisture.^4,5 Sulfates are used as the primary detergents in the formulation of deep-cleaning shampoos, which are designed for people who accumulate a heavy buildup of dirt, sebum, and debris from frequent use of styling products. Due to their potent detergency, these shampoos typically are not used on a daily basis but rather at longer intervals.¹⁵ A downside to sulfates is that they can have cosmetically unpleasant properties, which can be compensated for by including appropriate softening additives in shampoo formulations.⁴ A number of anionic surfactants such as olefin sulfonate, alkyl sulfosuccinate, acyl peptides, and alkyl ether carboxylates are well tolerated by the skin and are used together with other anionic and amphoteric surfactants to optimize shampoo properties. Alternatively, sulfate-free shampoos are cleansers compounded by the removal of the anionic group and switched for surfactants with less detergency.^4,5

Preservatives and Parabens

Parabens refer to a group of esters of 4-hydroxybenzoic acid commonly used as preservatives in foods, pharmaceuticals, and cosmetics whose widespread use dates back to 1923.¹⁶ Concerns over the presence of parabens in shampoos and other cosmetics have been raised by patients for their reputed estrogenic and antiandrogenic effects and suspected involvement in carcinogenesis via endocrine modulation.^16,17 In in vitro studies done on yeast assays, parabens have shown weak estrogenic activity that increases in proportion to both the length and increased branching of the alkyl side chains in the paraben’s molecular structure.¹⁸ They are 10,000-fold less potent than 17β-estradiol. In in vivo animal studies, parabens show weak estrogenic activity and are 100,000-fold less potent than 17β-estradiol.¹⁸ 4-Hydroxybenzoic acid, a common metabolite, showed no estrogenic activity when tested both in vitro and in vivo.¹⁹ Some concerning research has implicated a link between parabens used in underarm cosmetics, such as deodorants and antiperspirants, and breast cancer¹⁶; however, the studies have been conflicting, and there is simply not enough data to assert that parabens cause breast cancer.

The Cosmetic Ingredient Review expert panel first reviewed parabens in 1984 and concluded that “methylparaben, ethylparaben, propylparaben, and butylparaben are safe as cosmetic ingredients in the present practices of use.”²⁰ They extended this statement to include isopropylparaben and isobutylparaben in a later review.²¹ In 2005, the Scientific Committee on Consumer Products (now known as the Scientific Committee for Consumer Safety) in Europe stated that methylparaben and ethylparaben can be used at levels up to 0.4% in products.²² This decision was reached due to reports of decreased sperm counts and testosterone levels in male juvenile rats exposed to these parabens; however, these reults were not successfully replicated in larger studies.^16,22 In 2010, the Scientific Committee for Consumer Safety revisited its stance on parabens, and they then revised their recommendations to say that concentrations of propylparaben and butylparaben should not exceed concentrations of 0.19%, based on “the conservative choice for the calculation of the [Margin-of-Safety] of butyl- and propylparaben.”²³ However, in 2011 the use of propylparaben and butylparaben was banned in Denmark for cosmetic products used in children 3 years or younger,¹⁶ and the European Commission subsequently amended their directive in 2014, banning isopropylparaben, isobutylparaben, phenylparaben, benzylparaben, and pentylparaben due to lack of data available to evaluate the human risk of these products.²⁴

Contrary to the trends in Europe, there currently are no regulations against the use of parabens in shampoos or other cosmetics in the United States. The American Cancer Society found that there is no evidence to suggest that the current levels of parabens in cosmetic products (eg, antiperspirants) increase one’s risk of breast cancer.²⁵ Parabens are readily absorbed into the body both transdermally and through ingestion but also are believed to be rapidly transformed into harmless and nonspecific metabolites; they are readily metabolized by the liver and excreted in urine, and there is no measured accumulation in tissues.¹⁷

Parabens continue to be the most widely used preservatives in personal care products, usually in conjunction with other preservatives. Parabens are good biocides; short-chain esters (eg, methylparabens, ethylparabens) are effective against gram-positive bacteria and are weakly effective against gram-negative bacteria. Long-chain paraben esters (eg, propylparabens, butylparabens) are effective against mold and yeast. The addition of other preservatives creates a broad spectrum of antimicrobial defense in consumer products. Other preservatives include formaldehyde releasers or phenoxyethanol, as well as chelating agents such as EDTA, which improve the stability of these cosmetic products when exposed to air.¹⁶ Parabens are naturally occurring substances found in foods such as blueberries, barley, strawberries, yeast, olives, and grapes. As a colorless, odorless, and inexpensive substance, their use has been heavily favored in cosmetic and food products.¹⁶

Shampoo Alternatives and the No-Poo Method

Although research has not demonstrated any long-term danger to using shampoo, certain chemicals found in shampoos have the potential to irritate the scalp. Commonly cited allergens in shampoos include cocamidopropyl betaine, propylene glycol, vitamin E (tocopherol), parabens, and benzophenones.⁵ Additionally, the rising use of formaldehyde-releasing preservatives and isothiazolinones due to mounting pressures to move away from parabens has led to an increase in cases of allergic contact dermatitis (ACD).¹⁶ However, the irritability (rather than allergenicity) of these substances often is established during patch testing, a method of detecting delayed-type allergic reactions, which is important to note because patch testing requires a substance to be exposed to the skin for 24 to 48 hours, whereas exposure to shampoo ingredients may last a matter of minutes at most and occur in lesser concentrations because the ingredients are diluted by water in the rinsing process. Given these differences, it is unlikely that a patient would develop a true allergic response from regular shampoo use. Nevertheless, in patients who are already sensitized, exposure could conceivably trigger ACD, and patients must be cognizant of the composition of their shampoos.¹⁶

The no-poo method refers to the avoidance of commercial shampoo products when cleansing the hair and scalp and encompasses different methods of cleansing the hair, such as the use of household items (eg, baking soda, apple cider vinegar [ACV]), the use of conditioners to wash the hair (also known as conditioner-only washing or co-washing), treating the scalp with tea tree oil, or simply rinsing the hair with water. Proponents of the no-poo method believe that abstaining from shampoo use leads to healthier hair, retained natural oils, and less exposure to supposedly dangerous chemicals such as parabens or sulfates.^2,3,26-28 However, there are no known studies in the literature that assess or support the hypotheses of the no-poo method.

Baking Soda and ACV
Baking soda (sodium bicarbonate) is a substance commonly found in the average household. It has been used in toothpaste formulas and cosmetic products and is known for its acid-neutralizing properties. Baking soda has been shown to have some antifungal and viricidal properties through an unknown mechanism of action.²⁸ It has gained popularity for its use as a means of reducing the appearance of excessive greasiness of the hair shafts. Users also have reported that when washing their hair with baking soda, they are able to achieve a clean scalp and hair that feels soft to the touch.^2,3,26,27,29 Despite these reports, users must beware of using baking soda without adequately diluting it with water. Baking soda is a known alkaline irritant.^26,30 With a pH of 9, baking soda causes the cuticle layer of the hair fiber to open, increasing the capacity for water absorption. Water penetrates the scales that open, breaking the hydrogen bonds of the keratin molecule.³¹ Keratin is a spiral helical molecule that keeps its shape due to hydrogen, disulfide, and ionic bonds, as well as Van der Waals force.³⁰ Hydrolysis of these bonds due to exposure to baking soda lowers the elasticity of the hair and increases the negative electrical net charge of the hair fiber surface, which leads to increased friction between fibers, cuticle damage, hair fragility, and fiber breakage.^32,33

Apple cider vinegar is an apple-derived acetic acid solution with a pH ranging from 3.1 to 5.²⁸ The pH range of ACV is considered to be ideal for hair by no-poo proponents, as it is similar to the natural pH of the scalp. Its acidic properties are responsible for its antimicrobial abilities, particularly its effectiveness against gram-negative bacteria.³⁰ The acetic acid of ACV can partially interrupt oil interfaces, which contributes to its mild ability to remove product residue and scalp buildup from the hair shaft; the acetic acid also tightens the cuticles on hair fibers.³³ Apple cider vinegar is used as a means of cleansing the hair and scalp by no-poo proponents^2,3,26; other uses for ACV include using it as a rinse following washing and/or conditioning of the hair or as a means of preserving color in color-treated hair. There also is evidence that ACV may have antifungal properties.²⁸ However, consumers must be aware that if it is not diluted in water, ACV may be too caustic for direct application to the hair and may lead to damage; it can be irritating to eyes, mucus membranes, and acutely inflamed skin. Also, vinegar rinses used on processed or chemically damaged hair may lead to increased hair fragility.^2,3

Hair fibers have a pH of 3.67, while the scalp has a pH between 4.5 and 6.2. This slightly acidic film acts as a barrier to viruses, bacteria, and other potential contaminants.³³ Studies have shown that the pH of skin increases in proportion to the pH of the cleanser used.³⁴ Therefore, due to the naturally acidic pH of the scalp, acid-balanced shampoos generally are recommended. Shampoos should not have a pH higher than 5.5, as hair shafts can swell due to alkalinization, which can be prevented by pH balancing the shampoo through the addition of an acidic substance (eg, glycolic acid, citric acid) to lower the pH down to approximately 5.5. Apple cider vinegar often is used for this purpose. However, one study revealed that 82% of shampoos already have an acidic pH.³⁴

Conditioner-Only Washing (Co-washing)
Conditioner-only washing, or co-washing, is a widely practiced method of hair grooming. It is popular among individuals who find that commercial shampoos strip too much of the natural hair oils away, leaving the hair rough or unmanageable. Co-washing is not harmful to the hair; however, the molecular structure and function of a conditioner and that of a shampoo are very different.^5,35,36 Conditioners are not formulated to remove dirt and buildup in the hair but rather to add substances to the hair, and thus cannot provide extensive cleansing of the hair and scalp; therefore, it is inappropriate to use co-washing as a replacement for shampooing. Quaternary conditioning agents are an exception because they contain amphoteric detergents comprised of both anionic and cationic groups, which allow them both the ability to remove dirt and sebum with its anionic group, typically found in shampoos, as well as the ability to coat and condition the hair due to the high affinity of the cationic group for the negatively charged hair fibers.^36,37 Amphoteric detergents are commonly found in 2-in-1 conditioning cleansers, among other ingredients, such as hydrolyzed animal proteins that temporarily plug surface defects on the hair fiber, and dimethicone, a synthetic oil that creates a thin film over the hair shaft, increasing shine and manageability. Of note, these conditioning shampoos are ideal for individuals with minimal product buildup on the hair and scalp and are not adequate scalp cleansers for individuals who either wash their hair infrequently or who regularly use hairstyling products.^36,37

Tea Tree Oil
Tea tree oil is an essential oil extracted from the Melaleuca alternifolia plant of the Myrtaceae family. It is native to the coast of northeastern Australia. A holy grail of natural cosmetics, tea tree oil is widely known for its antiviral, antifungal, and antiseptic properties.³⁸ Although not used as a stand-alone cleanser, it is often added to a number of cosmetic products, including shampoos and co-washes. Although deemed safe for topical use, it has been shown to be quite toxic when ingested. Symptoms of ingestion include nausea, vomiting, hallucinations, and coma. The common concern with tea tree oil is its ability to cause ACD. In particular, it is believed that the oxidation products of tea tree oil are allergenic rather than the tea tree oil itself. The evaluation of tea tree oil as a potential contact allergen has been quite difficult; it consists of more than 100 distinct compounds and is often mislabeled, or does not meet the guidelines of the International Organization for Standardization. Nonetheless, the prevalence of ACD due to tea tree oil is low (approximately 1.4%). Despite its low prevalence, tea tree oil should remain in the differential as an ACD-inducing agent. Patch testing with the patient’s supply of tea tree oil is advised when possible.³⁸

Conclusion

It is customary that the ingredients used in shampoos undergo periodic testing and monitoring to assure the safety of their use. Although it is encouraging that patients are proactive in their efforts to stay abreast of the literature, it is still important that cosmetic scientists, dermatologists, and other experts remain at the forefront of educating the public about these substances. Not doing so can result in the propagation of misinformation and unnecessary fears, which can lead to the adaptation of unhygienic or even unsafe hair care practices. As dermatologists, we must ensure that patients are educated about the benefits and hazards of off-label use of household ingredients to the extent that evidence-based medicine permits. Patients must be informed that not all synthetic substances are harmful, and likewise not all naturally occurring substances are safe.

The Diagnosis: Atypical Vascular Lesion

Atypical vascular lesion (AVL)(quiz image), named by Fineberg and Rosen,¹ is a vascular lesion that arises on mammary skin with a history of radiation exposure. Clinically, AVL can present as a papule or erythematous patch that manifests 3 to 7 years after radiation therapy.^2,3 There are 2 histologic subtypes of AVL: lymphatic and vascular.^2,4 Lymphatic-type AVL is comprised of a symmetric distribution of thin, dilated, and anastomosing vessels usually found in the superficial and mid dermis. The vessels are lined by flat or hobnail protuberant endothelial cells that lack nuclear irregularity or pleomorphism; however, hyperchromatism of endothelial cell nuclei is a common finding. Vascular-type AVL is morphologically similar to a capillary hemangioma, and histologic features include irregular growth of capillary-sized vessels that extend to the dermis and subcutis.^2,4 Atypical vascular lesions are benign lesions but may be a precursor to angiosarcoma. Along with vascular markers, D2-40 typically is positive. Surgical excision with clear margins is recommended when the lesion is small.^4,5 Observation is more appropriate for extensive lesions.

Angiosarcoma can arise spontaneously or in association with radiation or chronic lymphedema. Given the shared risk factors and presentation with AVL, it is essential to differentiate angiosarcoma from AVL. Primary cutaneous angiosarcoma usually presents on the head of elderly patients as an ecchymotic patch or plaque with ulceration.⁴ Secondary angiosarcoma may arise following radiation or chronic lymphedema (Stewart-Treves syndrome); however, some authors now prefer to consider lymphangiosarcoma arising in chronic lymphedematous limbs a distinct entity.⁶ Surgical excision with wide margins is the mainstay of therapy, but angiosarcoma has high recurrence rates, and the 5-year survival rate has been reported to be as low as 35%.⁷ Histologic overlap with AVL includes dissecting anastomosing vessels lined by hyperchromatic nuclei; however, angiosarcoma is distinguished by endothelial cell layering, nuclear pleomorphism, and prominent nucleoli (Figure 1).^4,8 Increased positivity for Ki-67 immunostain, which indicates cell proliferation, may be used to distinguish angiosarcoma from an AVL (Figure 1 [inset]).⁹ Further, in contrast to AVL, radiation-induced angiosarcoma is characterized by amplification of C-MYC, a regulator gene, and FLT4 (FMS-related tyrosine kinase 4), a gene encoding vascular endothelial growth factor receptor 3. Gene amplification may be detected through immunohistochemistry or fluorescence in situ hybridization.¹⁰ Ki-67 labeling showed less than 10% staining in endothelial cells in our case (quiz image [inset]), and fluorescence in situ hybridization was negative for C-MYC amplification, supporting the diagnosis of AVL.

Lymphangioma circumscriptum, the most common superficial lymphangioma, is a hamartomatous malformation that usually occurs at the axillary folds, neck, and trunk. It clinically presents as small agminated vesicles with a characteristic frog spawn appearance.¹¹ Dermoscopic features include yellow lacunae that may alternate with a dark red color secondary to extravasation of erythrocytes.¹² These clinical features often lead to a differential diagnosis of verrucae, angiokeratoma, and angiosarcoma. Lymphangioma circumscriptum histologically is characterized by an overgrowth of dilated lymphatic vessels that fill the papillary dermis. The vessels are composed of flat endothelial cells typically filled with acellular proteinaceous debris and occasional erythrocytes (Figure 2). As the lesion traverses deeper into the dermis, the caliber of the lymphatic channel becomes narrower. The presence of deep lymphatic cisterns with surrounding smooth muscle is helpful to differentiate lymphangioma circumscriptum from other lymphatic malformations such as acquired lymphangiectasia. Treatment options include surgical excision, sclerosing agents, and destructive modalities such as cryotherapy.

Hobnail hemangioma, originally termed targetoid hemosiderotic hemangioma by Santa Cruz and Aronberg,¹³ presents as a violaceous papule or nodule surrounded by a characteristic brown halo on the leg. Trauma has been proposed as the inciting factor for the clinical appearance of hobnail hemangioma.¹⁴ Microscopically, the lesion shows vessels in a wedge shape. The superficial component has telangiectatic vessels with focal areas of papillary projections lined by endothelial cells. Although the endothelial nuclei typically project into the lumen, the nuclei are small, bland, and without mitotic activity.¹⁵ Deeper components show slit-shaped vasculature with dermal collagen dissection. Hemosiderin, extravasated red blood cells, and inflammation are found adjacent to the vessels (Figure 3). Given the benign nature, hobnail hemangiomas may be monitored.

Kaposi sarcoma (KS) is a low-grade vascular neoplasm associated with human herpesvirus 8 that arises in multiple clinical settings, especially in immunosuppression secondary to human immunodeficiency virus. There are 3 distinct clinical stages: patch, plaque, and tumor. The patch stage appears as red macules that blend into larger plaques; the tumor stage is defined as larger nodules developing from plaques. Histologic features differ by stage. Similar to angiosarcoma, KS is comprised of anastomosing vessels that dissect collagen bundles; endothelial cell atypia is minimal. A useful feature of KS is its propensity to involve adnexa and display the promontory sign, which involves the tumor growing into normal vasculature (Figure 4).¹⁶ Positive immunohistochemistry for human herpesvirus 8 aids in confirmation of the diagnosis. Treatment options for KS are numerous but include destructive modalities, chemotherapeutic agents such as doxorubicin, or highly active antiretroviral therapy for AIDS-related KS.¹⁷

The Diagnosis: Atypical Vascular Lesion

Atypical vascular lesion (AVL)(quiz image), named by Fineberg and Rosen,¹ is a vascular lesion that arises on mammary skin with a history of radiation exposure. Clinically, AVL can present as a papule or erythematous patch that manifests 3 to 7 years after radiation therapy.^2,3 There are 2 histologic subtypes of AVL: lymphatic and vascular.^2,4 Lymphatic-type AVL is comprised of a symmetric distribution of thin, dilated, and anastomosing vessels usually found in the superficial and mid dermis. The vessels are lined by flat or hobnail protuberant endothelial cells that lack nuclear irregularity or pleomorphism; however, hyperchromatism of endothelial cell nuclei is a common finding. Vascular-type AVL is morphologically similar to a capillary hemangioma, and histologic features include irregular growth of capillary-sized vessels that extend to the dermis and subcutis.^2,4 Atypical vascular lesions are benign lesions but may be a precursor to angiosarcoma. Along with vascular markers, D2-40 typically is positive. Surgical excision with clear margins is recommended when the lesion is small.^4,5 Observation is more appropriate for extensive lesions.

Angiosarcoma can arise spontaneously or in association with radiation or chronic lymphedema. Given the shared risk factors and presentation with AVL, it is essential to differentiate angiosarcoma from AVL. Primary cutaneous angiosarcoma usually presents on the head of elderly patients as an ecchymotic patch or plaque with ulceration.⁴ Secondary angiosarcoma may arise following radiation or chronic lymphedema (Stewart-Treves syndrome); however, some authors now prefer to consider lymphangiosarcoma arising in chronic lymphedematous limbs a distinct entity.⁶ Surgical excision with wide margins is the mainstay of therapy, but angiosarcoma has high recurrence rates, and the 5-year survival rate has been reported to be as low as 35%.⁷ Histologic overlap with AVL includes dissecting anastomosing vessels lined by hyperchromatic nuclei; however, angiosarcoma is distinguished by endothelial cell layering, nuclear pleomorphism, and prominent nucleoli (Figure 1).^4,8 Increased positivity for Ki-67 immunostain, which indicates cell proliferation, may be used to distinguish angiosarcoma from an AVL (Figure 1 [inset]).⁹ Further, in contrast to AVL, radiation-induced angiosarcoma is characterized by amplification of C-MYC, a regulator gene, and FLT4 (FMS-related tyrosine kinase 4), a gene encoding vascular endothelial growth factor receptor 3. Gene amplification may be detected through immunohistochemistry or fluorescence in situ hybridization.¹⁰ Ki-67 labeling showed less than 10% staining in endothelial cells in our case (quiz image [inset]), and fluorescence in situ hybridization was negative for C-MYC amplification, supporting the diagnosis of AVL.

Lymphangioma circumscriptum, the most common superficial lymphangioma, is a hamartomatous malformation that usually occurs at the axillary folds, neck, and trunk. It clinically presents as small agminated vesicles with a characteristic frog spawn appearance.¹¹ Dermoscopic features include yellow lacunae that may alternate with a dark red color secondary to extravasation of erythrocytes.¹² These clinical features often lead to a differential diagnosis of verrucae, angiokeratoma, and angiosarcoma. Lymphangioma circumscriptum histologically is characterized by an overgrowth of dilated lymphatic vessels that fill the papillary dermis. The vessels are composed of flat endothelial cells typically filled with acellular proteinaceous debris and occasional erythrocytes (Figure 2). As the lesion traverses deeper into the dermis, the caliber of the lymphatic channel becomes narrower. The presence of deep lymphatic cisterns with surrounding smooth muscle is helpful to differentiate lymphangioma circumscriptum from other lymphatic malformations such as acquired lymphangiectasia. Treatment options include surgical excision, sclerosing agents, and destructive modalities such as cryotherapy.

Hobnail hemangioma, originally termed targetoid hemosiderotic hemangioma by Santa Cruz and Aronberg,¹³ presents as a violaceous papule or nodule surrounded by a characteristic brown halo on the leg. Trauma has been proposed as the inciting factor for the clinical appearance of hobnail hemangioma.¹⁴ Microscopically, the lesion shows vessels in a wedge shape. The superficial component has telangiectatic vessels with focal areas of papillary projections lined by endothelial cells. Although the endothelial nuclei typically project into the lumen, the nuclei are small, bland, and without mitotic activity.¹⁵ Deeper components show slit-shaped vasculature with dermal collagen dissection. Hemosiderin, extravasated red blood cells, and inflammation are found adjacent to the vessels (Figure 3). Given the benign nature, hobnail hemangiomas may be monitored.

Kaposi sarcoma (KS) is a low-grade vascular neoplasm associated with human herpesvirus 8 that arises in multiple clinical settings, especially in immunosuppression secondary to human immunodeficiency virus. There are 3 distinct clinical stages: patch, plaque, and tumor. The patch stage appears as red macules that blend into larger plaques; the tumor stage is defined as larger nodules developing from plaques. Histologic features differ by stage. Similar to angiosarcoma, KS is comprised of anastomosing vessels that dissect collagen bundles; endothelial cell atypia is minimal. A useful feature of KS is its propensity to involve adnexa and display the promontory sign, which involves the tumor growing into normal vasculature (Figure 4).¹⁶ Positive immunohistochemistry for human herpesvirus 8 aids in confirmation of the diagnosis. Treatment options for KS are numerous but include destructive modalities, chemotherapeutic agents such as doxorubicin, or highly active antiretroviral therapy for AIDS-related KS.¹⁷

The Diagnosis: Atypical Vascular Lesion

Atypical vascular lesion (AVL)(quiz image), named by Fineberg and Rosen,¹ is a vascular lesion that arises on mammary skin with a history of radiation exposure. Clinically, AVL can present as a papule or erythematous patch that manifests 3 to 7 years after radiation therapy.^2,3 There are 2 histologic subtypes of AVL: lymphatic and vascular.^2,4 Lymphatic-type AVL is comprised of a symmetric distribution of thin, dilated, and anastomosing vessels usually found in the superficial and mid dermis. The vessels are lined by flat or hobnail protuberant endothelial cells that lack nuclear irregularity or pleomorphism; however, hyperchromatism of endothelial cell nuclei is a common finding. Vascular-type AVL is morphologically similar to a capillary hemangioma, and histologic features include irregular growth of capillary-sized vessels that extend to the dermis and subcutis.^2,4 Atypical vascular lesions are benign lesions but may be a precursor to angiosarcoma. Along with vascular markers, D2-40 typically is positive. Surgical excision with clear margins is recommended when the lesion is small.^4,5 Observation is more appropriate for extensive lesions.

Angiosarcoma can arise spontaneously or in association with radiation or chronic lymphedema. Given the shared risk factors and presentation with AVL, it is essential to differentiate angiosarcoma from AVL. Primary cutaneous angiosarcoma usually presents on the head of elderly patients as an ecchymotic patch or plaque with ulceration.⁴ Secondary angiosarcoma may arise following radiation or chronic lymphedema (Stewart-Treves syndrome); however, some authors now prefer to consider lymphangiosarcoma arising in chronic lymphedematous limbs a distinct entity.⁶ Surgical excision with wide margins is the mainstay of therapy, but angiosarcoma has high recurrence rates, and the 5-year survival rate has been reported to be as low as 35%.⁷ Histologic overlap with AVL includes dissecting anastomosing vessels lined by hyperchromatic nuclei; however, angiosarcoma is distinguished by endothelial cell layering, nuclear pleomorphism, and prominent nucleoli (Figure 1).^4,8 Increased positivity for Ki-67 immunostain, which indicates cell proliferation, may be used to distinguish angiosarcoma from an AVL (Figure 1 [inset]).⁹ Further, in contrast to AVL, radiation-induced angiosarcoma is characterized by amplification of C-MYC, a regulator gene, and FLT4 (FMS-related tyrosine kinase 4), a gene encoding vascular endothelial growth factor receptor 3. Gene amplification may be detected through immunohistochemistry or fluorescence in situ hybridization.¹⁰ Ki-67 labeling showed less than 10% staining in endothelial cells in our case (quiz image [inset]), and fluorescence in situ hybridization was negative for C-MYC amplification, supporting the diagnosis of AVL.

Lymphangioma circumscriptum, the most common superficial lymphangioma, is a hamartomatous malformation that usually occurs at the axillary folds, neck, and trunk. It clinically presents as small agminated vesicles with a characteristic frog spawn appearance.¹¹ Dermoscopic features include yellow lacunae that may alternate with a dark red color secondary to extravasation of erythrocytes.¹² These clinical features often lead to a differential diagnosis of verrucae, angiokeratoma, and angiosarcoma. Lymphangioma circumscriptum histologically is characterized by an overgrowth of dilated lymphatic vessels that fill the papillary dermis. The vessels are composed of flat endothelial cells typically filled with acellular proteinaceous debris and occasional erythrocytes (Figure 2). As the lesion traverses deeper into the dermis, the caliber of the lymphatic channel becomes narrower. The presence of deep lymphatic cisterns with surrounding smooth muscle is helpful to differentiate lymphangioma circumscriptum from other lymphatic malformations such as acquired lymphangiectasia. Treatment options include surgical excision, sclerosing agents, and destructive modalities such as cryotherapy.

Hobnail hemangioma, originally termed targetoid hemosiderotic hemangioma by Santa Cruz and Aronberg,¹³ presents as a violaceous papule or nodule surrounded by a characteristic brown halo on the leg. Trauma has been proposed as the inciting factor for the clinical appearance of hobnail hemangioma.¹⁴ Microscopically, the lesion shows vessels in a wedge shape. The superficial component has telangiectatic vessels with focal areas of papillary projections lined by endothelial cells. Although the endothelial nuclei typically project into the lumen, the nuclei are small, bland, and without mitotic activity.¹⁵ Deeper components show slit-shaped vasculature with dermal collagen dissection. Hemosiderin, extravasated red blood cells, and inflammation are found adjacent to the vessels (Figure 3). Given the benign nature, hobnail hemangiomas may be monitored.

Kaposi sarcoma (KS) is a low-grade vascular neoplasm associated with human herpesvirus 8 that arises in multiple clinical settings, especially in immunosuppression secondary to human immunodeficiency virus. There are 3 distinct clinical stages: patch, plaque, and tumor. The patch stage appears as red macules that blend into larger plaques; the tumor stage is defined as larger nodules developing from plaques. Histologic features differ by stage. Similar to angiosarcoma, KS is comprised of anastomosing vessels that dissect collagen bundles; endothelial cell atypia is minimal. A useful feature of KS is its propensity to involve adnexa and display the promontory sign, which involves the tumor growing into normal vasculature (Figure 4).¹⁶ Positive immunohistochemistry for human herpesvirus 8 aids in confirmation of the diagnosis. Treatment options for KS are numerous but include destructive modalities, chemotherapeutic agents such as doxorubicin, or highly active antiretroviral therapy for AIDS-related KS.¹⁷

Dermoscopy increases diagnostic accuracy in the analysis of skin growths.^1,2 Recently the use of dermoscopy has broadened to include inflammatory dermatoses and skin infections.³ To substantiate the value of dermoscopy in assessing psoriasis, we performed a systematic review of the literature and briefly reviewed 31 articles. We also report a case that highlights the differences between psoriasis and basal cell carcinoma (BCC) under dermoscopic examination, and we discuss the literature on the dermoscopic findings of psoriasis with an emphasis on the relative sensitivities and specificities of dermoscopic findings for psoriasis and for BCC.

Case Report

A 63-year-old man with psoriasis and a history of BCC presented for follow-up of psoriasis, which was well-controlled on etanercept. The physical examination was remarkable for scaly pink papules scattered on the trunk and extremities. A new larger red-pink patch was located on the left lower back (Figure 1). Dermoscopic evaluation of the new patch revealed shiny white lines and branching blood vessels (Figure 2). Pathology results of a shave biopsy revealed superficial BCC. The skin cancer was treated with electrodesiccation and curettage.

Comment

The clinical morphology of psoriasis and BCC can be similar, and dermoscopy can help in differentiating between the 2 conditions.

Literature Search on Dermoscopy and Psoriasis
We performed a PubMed search of articles indexed for MEDLINE to review the published literature on dermoscopy and psoriasis. Two reviewers (C.H. and L.C.) searched for psoriasis paired with the terms dermoscopy or dermatoscopy or epiluminescence microscopy. Only English-language articles published between 1996 and 2016 were included in the search. Articles that focused solely on confocal microscopy were excluded. Article titles and abstracts were evaluated and articles that omitted mention of dermoscopy and psoriasis were excluded, yielding a total of 31 articles. Of these articles, only 2 discussed the specificity or sensitivity of the dermoscopic findings of psoriasis.^4,5 Most of the articles were case reports and descriptive cross-sectional studies. The reports addressed multiple subtypes of psoriasis, but reports on psoriasis vulgaris and scalp psoriasis were most common (Table). Lallas et al⁶ provided a comprehensive descriptive review of the main findings on dermoscopy for psoriasis and other inflammatory skin conditions, but it lacked a comparison between psoriasis and BCC or data on the sensitivity and specificity of the findings. Two studies reported sensitivity and specificity values for the dermoscopic findings of psoriasis.^4,5 Pan et al⁵ reported a 98% diagnostic probability of psoriasis if red dots, homogeneous vascular pattern, and a light red background are all present. Additionally, they reported that the presence of 4 of 6 criteria for BCC—scattered vascular pattern, arborizing microvessels, telangiectatic or atypical vessels, milky-pink background, and brown dots⁄globules—yielded a diagnostic probability of 99%.⁵ Similarly, Lallas et al⁶ demonstrated that the presence of dotted vessels alone is not sufficient to presume a diagnosis of psoriasis, as this finding can be seen in other inflammatory skin conditions. However, “the combination of regularly distributed dotted vessels over a light red background associated with diffuse white scales was highly predictive of [plaque psoriasis] and allowed a correct diagnosis with 88.0% specificity and 84.9% sensitivity.”⁴ Figure 3 shows a dermoscopic image of plaque psoriasis that demonstrates these findings. The remaining literature corroborated this evidence, with the most commonly reported dermoscopic findings of psoriasis being red dots, red globules, glomerular vessels (also known as twisted capillary loops), red globular rings, and white scale.^7-12

Dermoscopy and BCC
Much has been published on the dermoscopic findings of BCC.^5,13-15 The dermoscopic findings of BCC include large blue-gray ovoid nests, leaflike areas, spoke-wheel–like areas, arborizing vessels (telangiectasia), and ulceration.¹⁵ Superficial BCC is characterized by short fine or arborizing telangiectasia, shallow erosions, and shiny white areas.¹⁵ The positive predictive value of dermoscopy in BCC is as high as 97%.¹⁶ Additionally, multiple studies report a sensitivity of 95% to 99%^5,13,14 and a specificity of 79% to 99% in the use of dermoscopy for identifying BCC. According to Pan et al,⁵ the most sensitive finding for BCC is a scattered vascular pattern (97%), while the most specific finding is arborizing microvessels (99%).

Utility of Dermoscopy
Our case of a 63-year-old man with a history of psoriasis and BCC highlights the usefulness of dermoscopy in accurately determining the features of each condition. Additionally, dermoscopy aids in differentiating between psoriasis and squamous cell carcinoma. In contrast to the dotted vessels seen in psoriasis, squamous cell carcinomas often have peripheral hairpin (glomerular) vessels.¹⁷

If future reports confirm dermoscopy’s utility in accurately diagnosing psoriasis, fewer biopsies may be needed when evaluating patients with new rashes. Furthermore, dermoscopy may expedite treatment of psoriasis (as it can for malignant conditions) by obviating the wait for pathology results currently needed to initiate systemic treatment. For patients with psoriasis who also have sun-damaged skin, dermoscopy may assist in differentiating pink patches and plaques of psoriasis from skin cancer, such as superficial BCCs, which often have shiny white lines not seen in psoriasis.¹⁵

Dermoscopy increases diagnostic accuracy in the analysis of skin growths.^1,2 Recently the use of dermoscopy has broadened to include inflammatory dermatoses and skin infections.³ To substantiate the value of dermoscopy in assessing psoriasis, we performed a systematic review of the literature and briefly reviewed 31 articles. We also report a case that highlights the differences between psoriasis and basal cell carcinoma (BCC) under dermoscopic examination, and we discuss the literature on the dermoscopic findings of psoriasis with an emphasis on the relative sensitivities and specificities of dermoscopic findings for psoriasis and for BCC.

Case Report

A 63-year-old man with psoriasis and a history of BCC presented for follow-up of psoriasis, which was well-controlled on etanercept. The physical examination was remarkable for scaly pink papules scattered on the trunk and extremities. A new larger red-pink patch was located on the left lower back (Figure 1). Dermoscopic evaluation of the new patch revealed shiny white lines and branching blood vessels (Figure 2). Pathology results of a shave biopsy revealed superficial BCC. The skin cancer was treated with electrodesiccation and curettage.

Comment

The clinical morphology of psoriasis and BCC can be similar, and dermoscopy can help in differentiating between the 2 conditions.

Literature Search on Dermoscopy and Psoriasis
We performed a PubMed search of articles indexed for MEDLINE to review the published literature on dermoscopy and psoriasis. Two reviewers (C.H. and L.C.) searched for psoriasis paired with the terms dermoscopy or dermatoscopy or epiluminescence microscopy. Only English-language articles published between 1996 and 2016 were included in the search. Articles that focused solely on confocal microscopy were excluded. Article titles and abstracts were evaluated and articles that omitted mention of dermoscopy and psoriasis were excluded, yielding a total of 31 articles. Of these articles, only 2 discussed the specificity or sensitivity of the dermoscopic findings of psoriasis.^4,5 Most of the articles were case reports and descriptive cross-sectional studies. The reports addressed multiple subtypes of psoriasis, but reports on psoriasis vulgaris and scalp psoriasis were most common (Table). Lallas et al⁶ provided a comprehensive descriptive review of the main findings on dermoscopy for psoriasis and other inflammatory skin conditions, but it lacked a comparison between psoriasis and BCC or data on the sensitivity and specificity of the findings. Two studies reported sensitivity and specificity values for the dermoscopic findings of psoriasis.^4,5 Pan et al⁵ reported a 98% diagnostic probability of psoriasis if red dots, homogeneous vascular pattern, and a light red background are all present. Additionally, they reported that the presence of 4 of 6 criteria for BCC—scattered vascular pattern, arborizing microvessels, telangiectatic or atypical vessels, milky-pink background, and brown dots⁄globules—yielded a diagnostic probability of 99%.⁵ Similarly, Lallas et al⁶ demonstrated that the presence of dotted vessels alone is not sufficient to presume a diagnosis of psoriasis, as this finding can be seen in other inflammatory skin conditions. However, “the combination of regularly distributed dotted vessels over a light red background associated with diffuse white scales was highly predictive of [plaque psoriasis] and allowed a correct diagnosis with 88.0% specificity and 84.9% sensitivity.”⁴ Figure 3 shows a dermoscopic image of plaque psoriasis that demonstrates these findings. The remaining literature corroborated this evidence, with the most commonly reported dermoscopic findings of psoriasis being red dots, red globules, glomerular vessels (also known as twisted capillary loops), red globular rings, and white scale.^7-12

Dermoscopy and BCC
Much has been published on the dermoscopic findings of BCC.^5,13-15 The dermoscopic findings of BCC include large blue-gray ovoid nests, leaflike areas, spoke-wheel–like areas, arborizing vessels (telangiectasia), and ulceration.¹⁵ Superficial BCC is characterized by short fine or arborizing telangiectasia, shallow erosions, and shiny white areas.¹⁵ The positive predictive value of dermoscopy in BCC is as high as 97%.¹⁶ Additionally, multiple studies report a sensitivity of 95% to 99%^5,13,14 and a specificity of 79% to 99% in the use of dermoscopy for identifying BCC. According to Pan et al,⁵ the most sensitive finding for BCC is a scattered vascular pattern (97%), while the most specific finding is arborizing microvessels (99%).

Utility of Dermoscopy
Our case of a 63-year-old man with a history of psoriasis and BCC highlights the usefulness of dermoscopy in accurately determining the features of each condition. Additionally, dermoscopy aids in differentiating between psoriasis and squamous cell carcinoma. In contrast to the dotted vessels seen in psoriasis, squamous cell carcinomas often have peripheral hairpin (glomerular) vessels.¹⁷

If future reports confirm dermoscopy’s utility in accurately diagnosing psoriasis, fewer biopsies may be needed when evaluating patients with new rashes. Furthermore, dermoscopy may expedite treatment of psoriasis (as it can for malignant conditions) by obviating the wait for pathology results currently needed to initiate systemic treatment. For patients with psoriasis who also have sun-damaged skin, dermoscopy may assist in differentiating pink patches and plaques of psoriasis from skin cancer, such as superficial BCCs, which often have shiny white lines not seen in psoriasis.¹⁵

Dermoscopy increases diagnostic accuracy in the analysis of skin growths.^1,2 Recently the use of dermoscopy has broadened to include inflammatory dermatoses and skin infections.³ To substantiate the value of dermoscopy in assessing psoriasis, we performed a systematic review of the literature and briefly reviewed 31 articles. We also report a case that highlights the differences between psoriasis and basal cell carcinoma (BCC) under dermoscopic examination, and we discuss the literature on the dermoscopic findings of psoriasis with an emphasis on the relative sensitivities and specificities of dermoscopic findings for psoriasis and for BCC.

Case Report

A 63-year-old man with psoriasis and a history of BCC presented for follow-up of psoriasis, which was well-controlled on etanercept. The physical examination was remarkable for scaly pink papules scattered on the trunk and extremities. A new larger red-pink patch was located on the left lower back (Figure 1). Dermoscopic evaluation of the new patch revealed shiny white lines and branching blood vessels (Figure 2). Pathology results of a shave biopsy revealed superficial BCC. The skin cancer was treated with electrodesiccation and curettage.

Comment

The clinical morphology of psoriasis and BCC can be similar, and dermoscopy can help in differentiating between the 2 conditions.

Literature Search on Dermoscopy and Psoriasis
We performed a PubMed search of articles indexed for MEDLINE to review the published literature on dermoscopy and psoriasis. Two reviewers (C.H. and L.C.) searched for psoriasis paired with the terms dermoscopy or dermatoscopy or epiluminescence microscopy. Only English-language articles published between 1996 and 2016 were included in the search. Articles that focused solely on confocal microscopy were excluded. Article titles and abstracts were evaluated and articles that omitted mention of dermoscopy and psoriasis were excluded, yielding a total of 31 articles. Of these articles, only 2 discussed the specificity or sensitivity of the dermoscopic findings of psoriasis.^4,5 Most of the articles were case reports and descriptive cross-sectional studies. The reports addressed multiple subtypes of psoriasis, but reports on psoriasis vulgaris and scalp psoriasis were most common (Table). Lallas et al⁶ provided a comprehensive descriptive review of the main findings on dermoscopy for psoriasis and other inflammatory skin conditions, but it lacked a comparison between psoriasis and BCC or data on the sensitivity and specificity of the findings. Two studies reported sensitivity and specificity values for the dermoscopic findings of psoriasis.^4,5 Pan et al⁵ reported a 98% diagnostic probability of psoriasis if red dots, homogeneous vascular pattern, and a light red background are all present. Additionally, they reported that the presence of 4 of 6 criteria for BCC—scattered vascular pattern, arborizing microvessels, telangiectatic or atypical vessels, milky-pink background, and brown dots⁄globules—yielded a diagnostic probability of 99%.⁵ Similarly, Lallas et al⁶ demonstrated that the presence of dotted vessels alone is not sufficient to presume a diagnosis of psoriasis, as this finding can be seen in other inflammatory skin conditions. However, “the combination of regularly distributed dotted vessels over a light red background associated with diffuse white scales was highly predictive of [plaque psoriasis] and allowed a correct diagnosis with 88.0% specificity and 84.9% sensitivity.”⁴ Figure 3 shows a dermoscopic image of plaque psoriasis that demonstrates these findings. The remaining literature corroborated this evidence, with the most commonly reported dermoscopic findings of psoriasis being red dots, red globules, glomerular vessels (also known as twisted capillary loops), red globular rings, and white scale.^7-12

Dermoscopy and BCC
Much has been published on the dermoscopic findings of BCC.^5,13-15 The dermoscopic findings of BCC include large blue-gray ovoid nests, leaflike areas, spoke-wheel–like areas, arborizing vessels (telangiectasia), and ulceration.¹⁵ Superficial BCC is characterized by short fine or arborizing telangiectasia, shallow erosions, and shiny white areas.¹⁵ The positive predictive value of dermoscopy in BCC is as high as 97%.¹⁶ Additionally, multiple studies report a sensitivity of 95% to 99%^5,13,14 and a specificity of 79% to 99% in the use of dermoscopy for identifying BCC. According to Pan et al,⁵ the most sensitive finding for BCC is a scattered vascular pattern (97%), while the most specific finding is arborizing microvessels (99%).

Utility of Dermoscopy
Our case of a 63-year-old man with a history of psoriasis and BCC highlights the usefulness of dermoscopy in accurately determining the features of each condition. Additionally, dermoscopy aids in differentiating between psoriasis and squamous cell carcinoma. In contrast to the dotted vessels seen in psoriasis, squamous cell carcinomas often have peripheral hairpin (glomerular) vessels.¹⁷

If future reports confirm dermoscopy’s utility in accurately diagnosing psoriasis, fewer biopsies may be needed when evaluating patients with new rashes. Furthermore, dermoscopy may expedite treatment of psoriasis (as it can for malignant conditions) by obviating the wait for pathology results currently needed to initiate systemic treatment. For patients with psoriasis who also have sun-damaged skin, dermoscopy may assist in differentiating pink patches and plaques of psoriasis from skin cancer, such as superficial BCCs, which often have shiny white lines not seen in psoriasis.¹⁵

The Diagnosis: Necrobiotic Xanthogranuloma

A 4-mm punch biopsy was performed for routine stain with hematoxylin and eosin. The differential diagnosis included sarcoidosis, necrobiosis lipoidica, xanthoma disseminatum, and multicentric reticulohistiocytosis. Histopathologic examination demonstrated a dermal infiltrate of foamy histiocytes and neutrophils (Figure). There were surrounding areas of degenerated collagen containing numerous cholesterol clefts. After clinical pathologic correlation, a diagnosis of necrobiotic xanthogranuloma (NXG) was elucidated.

The patient was referred to general surgery for elective excision of 1 or more of the lesions. Excision of an abdominal lesion was performed without complication. After several months, a new lesion reformed within the excisional scar that also was consistent with NXG. At further dermatologic visits, a trial of intralesional corticosteroids was attempted to the largest lesions with modest improvement. In addition, follow-up with hematology and oncology was recommended for routine surveillance of the known blood dyscrasia.

Necrobiotic xanthogranuloma is a multisystem non-Langerhans cell histiocytic disease. Clinically, NXG is characterized by infiltrative plaques and ulcerative nodules. Lesions may appear red, brown, or yellow with associated atrophy and telangiectasia.¹ Koch et al² described a predilection for granuloma formation within preexisting scars. Periorbital location is the most common cutaneous site of involvement of NXG, seen in 80% of cases, but the trunk and extremities also may be involved.^1,3 Approximately half of those with periocular involvement experience ocular symptoms including prop- tosis, blepharoptosis, and restricted eye movements.⁴ The onset of NXG most commonly is seen in middle age.

Characteristic systemic associations have been reported in the setting of NXG. More than 20% of patients may exhibit hepatomegaly. Hematologic abnormalities, hyperlipidemia, and cryoglobulinemia also may be seen.¹ In addition, a monoclonal gammopathy of uncertain significance is found in more than 80% of NXG cases. The IgG κ light chain is most commonly identified.² A foreign body reaction is incited by the immunoglobulin-lipid complex, which is thought to contribute to the formation of cutaneous lesions. There may be associated plasma cell dyscrasia such as multiple myeloma or B-cell lymphoma in approximately 13% of cases.² Evaluation for underlying plasma cell dyscrasia or lymphoproliferative disorder should be performed regularly with serum protein electrophoresis or immunofixation electrophoresis, and in some cases full-body imaging with computed tomography or magnetic resonance imaging may be warranted.¹

Treatment of NXG often is unsuccessful. Surgical excision, systemic immunosuppressive agents, electron beam radiation, and destructive therapies such as cryotherapy may be trialed, often with little success.¹ Cutaneous regression has been reported with combination treatment of high-dose dexamethasone and high-dose lenalidomide.⁵

The Diagnosis: Necrobiotic Xanthogranuloma

A 4-mm punch biopsy was performed for routine stain with hematoxylin and eosin. The differential diagnosis included sarcoidosis, necrobiosis lipoidica, xanthoma disseminatum, and multicentric reticulohistiocytosis. Histopathologic examination demonstrated a dermal infiltrate of foamy histiocytes and neutrophils (Figure). There were surrounding areas of degenerated collagen containing numerous cholesterol clefts. After clinical pathologic correlation, a diagnosis of necrobiotic xanthogranuloma (NXG) was elucidated.

The patient was referred to general surgery for elective excision of 1 or more of the lesions. Excision of an abdominal lesion was performed without complication. After several months, a new lesion reformed within the excisional scar that also was consistent with NXG. At further dermatologic visits, a trial of intralesional corticosteroids was attempted to the largest lesions with modest improvement. In addition, follow-up with hematology and oncology was recommended for routine surveillance of the known blood dyscrasia.

Necrobiotic xanthogranuloma is a multisystem non-Langerhans cell histiocytic disease. Clinically, NXG is characterized by infiltrative plaques and ulcerative nodules. Lesions may appear red, brown, or yellow with associated atrophy and telangiectasia.¹ Koch et al² described a predilection for granuloma formation within preexisting scars. Periorbital location is the most common cutaneous site of involvement of NXG, seen in 80% of cases, but the trunk and extremities also may be involved.^1,3 Approximately half of those with periocular involvement experience ocular symptoms including prop- tosis, blepharoptosis, and restricted eye movements.⁴ The onset of NXG most commonly is seen in middle age.

Characteristic systemic associations have been reported in the setting of NXG. More than 20% of patients may exhibit hepatomegaly. Hematologic abnormalities, hyperlipidemia, and cryoglobulinemia also may be seen.¹ In addition, a monoclonal gammopathy of uncertain significance is found in more than 80% of NXG cases. The IgG κ light chain is most commonly identified.² A foreign body reaction is incited by the immunoglobulin-lipid complex, which is thought to contribute to the formation of cutaneous lesions. There may be associated plasma cell dyscrasia such as multiple myeloma or B-cell lymphoma in approximately 13% of cases.² Evaluation for underlying plasma cell dyscrasia or lymphoproliferative disorder should be performed regularly with serum protein electrophoresis or immunofixation electrophoresis, and in some cases full-body imaging with computed tomography or magnetic resonance imaging may be warranted.¹

Treatment of NXG often is unsuccessful. Surgical excision, systemic immunosuppressive agents, electron beam radiation, and destructive therapies such as cryotherapy may be trialed, often with little success.¹ Cutaneous regression has been reported with combination treatment of high-dose dexamethasone and high-dose lenalidomide.⁵

The Diagnosis: Necrobiotic Xanthogranuloma

A 4-mm punch biopsy was performed for routine stain with hematoxylin and eosin. The differential diagnosis included sarcoidosis, necrobiosis lipoidica, xanthoma disseminatum, and multicentric reticulohistiocytosis. Histopathologic examination demonstrated a dermal infiltrate of foamy histiocytes and neutrophils (Figure). There were surrounding areas of degenerated collagen containing numerous cholesterol clefts. After clinical pathologic correlation, a diagnosis of necrobiotic xanthogranuloma (NXG) was elucidated.

The patient was referred to general surgery for elective excision of 1 or more of the lesions. Excision of an abdominal lesion was performed without complication. After several months, a new lesion reformed within the excisional scar that also was consistent with NXG. At further dermatologic visits, a trial of intralesional corticosteroids was attempted to the largest lesions with modest improvement. In addition, follow-up with hematology and oncology was recommended for routine surveillance of the known blood dyscrasia.

Necrobiotic xanthogranuloma is a multisystem non-Langerhans cell histiocytic disease. Clinically, NXG is characterized by infiltrative plaques and ulcerative nodules. Lesions may appear red, brown, or yellow with associated atrophy and telangiectasia.¹ Koch et al² described a predilection for granuloma formation within preexisting scars. Periorbital location is the most common cutaneous site of involvement of NXG, seen in 80% of cases, but the trunk and extremities also may be involved.^1,3 Approximately half of those with periocular involvement experience ocular symptoms including prop- tosis, blepharoptosis, and restricted eye movements.⁴ The onset of NXG most commonly is seen in middle age.

Characteristic systemic associations have been reported in the setting of NXG. More than 20% of patients may exhibit hepatomegaly. Hematologic abnormalities, hyperlipidemia, and cryoglobulinemia also may be seen.¹ In addition, a monoclonal gammopathy of uncertain significance is found in more than 80% of NXG cases. The IgG κ light chain is most commonly identified.² A foreign body reaction is incited by the immunoglobulin-lipid complex, which is thought to contribute to the formation of cutaneous lesions. There may be associated plasma cell dyscrasia such as multiple myeloma or B-cell lymphoma in approximately 13% of cases.² Evaluation for underlying plasma cell dyscrasia or lymphoproliferative disorder should be performed regularly with serum protein electrophoresis or immunofixation electrophoresis, and in some cases full-body imaging with computed tomography or magnetic resonance imaging may be warranted.¹

Treatment of NXG often is unsuccessful. Surgical excision, systemic immunosuppressive agents, electron beam radiation, and destructive therapies such as cryotherapy may be trialed, often with little success.¹ Cutaneous regression has been reported with combination treatment of high-dose dexamethasone and high-dose lenalidomide.⁵

Regenerative medicine encompasses innovative therapies that allow the body to repair or regenerate aging cells, tissues, and organs. The skin is a particularly attractive organ for the application of novel regenerative therapies due to its easy accessibility. Among these therapies, stem cells and platelet-rich plasma (PRP) have garnered interest based on their therapeutic potential in scar reduction, antiaging effects, and treatment of alopecia.

Stem cells possess the cardinal features of self-renewal and plasticity. Self-renewal refers to symmetric cell division generating daughter cells identical to the parent cell.¹ Plasticity is the ability to generate cell types other than the germ line or tissue lineage from which stem cells derive.² Stem cells can be categorized according to their differentiation potential. Totipotent stem cells may develop into any primary germ cell layer (ectoderm, mesoderm, endoderm) of the embryo, as well as extraembryonic tissue such as the trophoblast, which gives rise to the placenta. Pluripotent stem cells such as embryonic stem cells have the capacity to differentiate into any derivative of the 3 germ cell layers but have lost their ability to differentiate into the trophoblast.³ Adults lack totipotent or pluripotent cells; they have multipotent or unipotent cells. Multipotent stem cells are able to differentiate into multiple cell types from similar lineages; mesenchymal stem cells (MSCs), for example, can differentiate into adipogenic, osteogenic, chondrogenic, and myogenic cells.⁴ Unipotent stem cells have the lowest differentiation potential and can only self-regenerate. Herein, we review stem cell sources and their therapeutic potential in aesthetic dermatology.

Multipotent Stem Cells

Multipotent stem cells derived from the bone marrow, umbilical cord, adipose tissue, dermis, or hair follicle bulge have various clinical applications in dermatology. Stem cells from these sources are primarily utilized in an autologous manner in which they are processed outside the body and reintroduced into the donor. Autologous multipotent hematopoietic bone marrow cells were first successfully used for the treatment of chronic wounds and show promise for the treatment of atrophic scars.^5,6 However, due to the invasive nature of extracting bone marrow stem cells and their declining number with age, other sources of multipotent stem cells have fallen into favor.

Umbilical cord blood is a source of multipotent hematopoietic stem cells for which surgical intervention is not necessary because they are retrieved after umbilical cord clamping.⁷ Advantages of sourcing stem cells from umbilical cord blood includes high regenerative power compared to a newborn’s skin and low immunogenicity given that the newborn is immunologically immature.⁸

Another popular source for autologous stem cells is adipose tissue due to its ease of accessibility and relative abundance. Given that adipose tissue–derived stem cells (ASCs) are capable of differentiating into adipocytes that help maintain volume over time, they are being used for midface contouring, lip augmentation, facial rejuvenation, facial scarring, lipodystrophy, penile girth enhancement, and vaginal augmentation. Adipose tissue–derived stem cells also are capable of differentiating into other types of tissue, including cartilage and bone. Thus, they have been successfully harnessed in the treatment of patients affected by systemic sclerosis and Parry-Romberg syndrome as well in the functional and aesthetic reconstruction of various military combat–related deformities.^9,10

Adipose tissue–derived stem cells are commonly harvested from lipoaspirate of the abdomen and are combined with supportive mechanical scaffolds such as hydrogels. Lipoaspirate itself can serve as a scaffold for ASCs. Accordingly, ASCs also are being utilized as a scaffold for autologous fat transfer procedures in an effort to increase the viability of transplanted donor tissue, a process known as cell-assisted lipotransfer (CAL). In CAL, a fraction of the aspirated fat is processed for isolation of ASCs, which are then recombined with the remainder of the aspirated fat prior to grafting.¹¹ However, there is conflicting evidence as to whether CAL leads to improved graft success relative to conventional autologous fat transfer.^12,13

The skin also serves as an easily accessible and abundant autologous source of stem cells. A subtype of dermal fibroblasts has been proven to have multipotent potential.^14,15 These dermal fibroblasts are harvested from one area of the skin using punch biopsy and are processed and reinjected into another desired area of the skin.¹⁶ Autologous human fibroblasts have proven to be effective for the treatment of wrinkles, rhytides, and acne scars.¹⁷ In June 2011, the US Food and Drug Administration approved azficel-T, an autologous cellular product created by harvesting fibroblasts from a patient’s own postauricular skin, culture-expanding them in vitro for 3 months, and reinjecting the cells into the desired area of dermis in a series of treatments. This product was the first personalized cell therapy approved by the US Food and Drug Administration for aesthetic uses, specifically for the improvement of nasolabial fold wrinkles.¹⁸

In adults, hair follicles contain an area known as the bulge, which is a site rich in epithelial and melanocytic stem cells. Bulge stem cells have the ability to reproduce the interfollicular epidermis, hair follicle structures, and sebaceous glands, and they have been used to construct entirely new hair follicles in an artificial in vivo system.¹⁹ Sugiyama-Nakagiri et al²⁰ demonstrated that an entire hair follicle epithelium and interfollicular epidermis can be regenerated using cultured bulge stem cells. The cultured bulge stem cells were mixed with dermal papilla cells from neonatal rat vibrissae and engrafted into a silicone chamber implanted on the backs of severe combined immune deficient (SCID) mice. The grafts exhibited tufts of hair as well as a complete interfollicular epidermis at 4 weeks after transplantation.²⁰ Thus, these bulge stem cells have the potential to treat male androgenic alopecia and female pattern hair loss. Bulge stem cells also have been shown to accelerate wound healing.²¹ Additionally, autologous melanocytic stem cells located at the hair follicle bulge are effective for treating vitiligo and are being investigated for the treatment of hair graying.²²

Induced Pluripotent Stem Cells

Given the ethical concerns that surround the procurement and use of embryonic stem cells, efforts have been made to retrieve pluripotent stem cells from adults. A major breakthrough occurred in 2006 when researchers altered the genes of specialized adult mouse cells to cause dedifferentiation and the return to an embryoniclike stem cell state.²³ Mouse somatic cells were reprogrammed through the activation of a combination of transcription factors. The resulting cells were termed induced pluripotent stem cells (iPSCs) and have since been recreated in human cell lines. The discovery of iPSCs precipitated a translational science revolution. Physician-scientists sought ways to apply the reprogrammed cells to the pathophysiology of obscure diseases, examination of drug targets, and regeneration of human tissue.²⁴ Tissue regeneration via induced naïve somatic cells has shown promise as a future method to treat neurologic, cardiovascular, and ophthalmologic diseases.²⁵

As the technology of cultivating and identifying optimal sources of iPSCs continues to advance, stem cell–based treatments have evolved as leading prospects in the field of biogerontology.^26-29 Although much of the research in antiaging medicine has utilized iPSCs to reprogram cell senescence, the altering of iPSCs at a cellular level also allows for the stimulation of collagen synthesis. This potential for collagen generation may have direct applicability in dermatologic practice, particularly for aesthetic treatments.

Much of the research into iPSC-derived collagen has focused on genodermatoses. Itoh et al³⁰ examined the creation of collagen through iPSCs to identify possible treatments for recessive dystrophic epidermolysis bullosa (DEB). Recessive DEB is characterized by mutations in the COL7A1 gene, which encodes type VII collagen, a basement membrane protein and component of the anchoring fibrils essential for skin integrity.³¹ Itoh et al³⁰ began with source cells obtained from a skin biopsy. The cells were dedifferentiated to iPSCs and then induced into dermal fibroblasts according to the methods established in prior studies of embryonic stem cells, namely with the use of ascorbic acid and transforming growth factor b. The newly formed fibroblasts were determined to be functional based on their ability to synthesize mature type VII collagen.³⁰ Once the viability of the iPSC-derived fibroblasts was confirmed in vitro, the cells were further tested through combination with human keratinocytes on SCID mice. The human keratinocytes grew together with the iPSC-derived fibroblasts, producing type VII collagen in the basement membrane zone and creating an epidermis with the normal markers.³⁰ Similarly, Robbins et al³² utilized SCID mice to successfully demonstrate that the transfection of keratinocytes from patients with junctional epidermolysis bullosa into SCID mice produced phenotypically normal skin.

Sebastiano et al³³ combined the concepts of iPSCs and genome editing in another study of recessive DEB. The investigators first cultured iPSCs from biopsies of affected patients. After deriving iPSCs and correcting their mutation via adenovirus-associated viral gene editing, the COL7A1 mutation-free cells were differentiated into keratinocytes. These iPSC-derived keratinocytes were subsequently grafted onto mice, which led to the production of wild-type collagen VII and a stratified epidermis. Despite this successful outcome, the grafts of iPSC-derived epidermis did not survive longer than 1 month.³³

One of the many obstacles facing the practical use of stem cells is their successful incorporation into human tissue. A possible solution was uncovered by Zhang et al³⁴ who examined iPSC-derived MSCs. Mesenchymal stem cells communicate via paracrine mechanisms, whereby exosomes containing RNA and proteins are released to potentiate a regenerative effect.³⁵ Zhang et al³⁴ found that injecting exosomes from human iPSC-derived MSCs into the wound sites of rats stimulated the production of type I collagen, type III collagen, and elastin. The wound sites demonstrated accelerated closure, narrower scar widths, and increased collagen maturity.

Understanding the role that local environment plays in stem cell differentiation, Xu et al³⁶ aimed to create an extracellular scaffold to induce fibroblast behavior from iPSCs. The authors engineered a framework similar to the normal extracellular membrane using proteoglycans, glycosaminoglycans, fibrinogen, and connective tissue growth factor. The iPSCs were then applied to the scaffolding, which led to successful fibroblast differentiation and type I collagen synthesis.³⁶ This use of local biosignaling cues holds important ramifications for controlling the fate of stem cells that have been introduced into a new environment.

Although the application of iPSCs in clinical dermatology has yet to be achieved, progress in the field is moving at a rapid pace. Several logistical elements require further mastery before therapeutics can be delivered. These areas include the optimal environment for iPSC differentiation, methods for maximization of graft survival, and different modes of transplanting iPSC-derived cells into patients. In cosmetic practice, success will depend on intradermal injections of collagen-producing iPSC-derived cells that possess long-term proliferative potential. Current research in mice models has demonstrated viability up to 16 weeks after intradermal injection of such cells.³⁷

Plant Stem Cells

In discussing the dermatologic applications of stem cell technology, clinicians should be aware of the plant stem cell products that have become a popular cosmeceutical trend. Companies advertise plant cells as a natural source of regenerative cells that can induce rejuvenation in human skin; however, there are no significant data to indicate that plant stem cells encourage or activate cellular growth in humans. Indeed, for stem cells to differentiate and produce viable components, the cells must first be incorporated as living components in the host tissue. Because plant stem cells do not survive in human tissue and plant cell cytokines fail to interact with the receptors on human cells, their current value in cosmeceuticals may be overstated.

Platelet-Rich Plasma

Platelet-rich plasma also is commonly associated with stem cell therapy, as PRP is known to potentiate stem cell proliferation, migration, and differentiation. However, PRP does not contain stem cells and is instead autologous plasma concentrated with platelets. In fact, platelets cannot even be classified as cells given that they lack a nucleus; platelets are considered cell fragments. The regenerative potential of PRP can be attributed to the growth factors released from platelets, which play an important role in tissue regeneration and repair. Platelet-rich plasma currently is being used in dermatology for skin rejuvenation (reduction of wrinkles and furrows) and treatment of acne scars.³⁸ There also is evidence supporting the effectiveness of PRP for alopecia and wound therapy, as growth factors play a vital role in hair growth and wound healing.³⁸ Apart from the use of PRP on its own, it can be used as a supplement to enhance the effects of antiaging procedures such as microneedling.³⁹

Future Directions

Multipotent stem cells and iPSCs discussed herein provide much promise in the field of regenerative dermatology. They are increasingly accessible and circumvent the use of ethically questionable embryonic stem cells. Although there is a general consensus on the great potential of stem cells for treating aesthetic skin conditions, high-quality randomized controlled trials remain scarce within the literature. Recognizing and optimizing these opportunities remains the next step in the future delivery of evidence-based care in regenerative dermatology.

Regenerative medicine encompasses innovative therapies that allow the body to repair or regenerate aging cells, tissues, and organs. The skin is a particularly attractive organ for the application of novel regenerative therapies due to its easy accessibility. Among these therapies, stem cells and platelet-rich plasma (PRP) have garnered interest based on their therapeutic potential in scar reduction, antiaging effects, and treatment of alopecia.

Stem cells possess the cardinal features of self-renewal and plasticity. Self-renewal refers to symmetric cell division generating daughter cells identical to the parent cell.¹ Plasticity is the ability to generate cell types other than the germ line or tissue lineage from which stem cells derive.² Stem cells can be categorized according to their differentiation potential. Totipotent stem cells may develop into any primary germ cell layer (ectoderm, mesoderm, endoderm) of the embryo, as well as extraembryonic tissue such as the trophoblast, which gives rise to the placenta. Pluripotent stem cells such as embryonic stem cells have the capacity to differentiate into any derivative of the 3 germ cell layers but have lost their ability to differentiate into the trophoblast.³ Adults lack totipotent or pluripotent cells; they have multipotent or unipotent cells. Multipotent stem cells are able to differentiate into multiple cell types from similar lineages; mesenchymal stem cells (MSCs), for example, can differentiate into adipogenic, osteogenic, chondrogenic, and myogenic cells.⁴ Unipotent stem cells have the lowest differentiation potential and can only self-regenerate. Herein, we review stem cell sources and their therapeutic potential in aesthetic dermatology.

Multipotent Stem Cells

Multipotent stem cells derived from the bone marrow, umbilical cord, adipose tissue, dermis, or hair follicle bulge have various clinical applications in dermatology. Stem cells from these sources are primarily utilized in an autologous manner in which they are processed outside the body and reintroduced into the donor. Autologous multipotent hematopoietic bone marrow cells were first successfully used for the treatment of chronic wounds and show promise for the treatment of atrophic scars.^5,6 However, due to the invasive nature of extracting bone marrow stem cells and their declining number with age, other sources of multipotent stem cells have fallen into favor.

Umbilical cord blood is a source of multipotent hematopoietic stem cells for which surgical intervention is not necessary because they are retrieved after umbilical cord clamping.⁷ Advantages of sourcing stem cells from umbilical cord blood includes high regenerative power compared to a newborn’s skin and low immunogenicity given that the newborn is immunologically immature.⁸

Another popular source for autologous stem cells is adipose tissue due to its ease of accessibility and relative abundance. Given that adipose tissue–derived stem cells (ASCs) are capable of differentiating into adipocytes that help maintain volume over time, they are being used for midface contouring, lip augmentation, facial rejuvenation, facial scarring, lipodystrophy, penile girth enhancement, and vaginal augmentation. Adipose tissue–derived stem cells also are capable of differentiating into other types of tissue, including cartilage and bone. Thus, they have been successfully harnessed in the treatment of patients affected by systemic sclerosis and Parry-Romberg syndrome as well in the functional and aesthetic reconstruction of various military combat–related deformities.^9,10

Adipose tissue–derived stem cells are commonly harvested from lipoaspirate of the abdomen and are combined with supportive mechanical scaffolds such as hydrogels. Lipoaspirate itself can serve as a scaffold for ASCs. Accordingly, ASCs also are being utilized as a scaffold for autologous fat transfer procedures in an effort to increase the viability of transplanted donor tissue, a process known as cell-assisted lipotransfer (CAL). In CAL, a fraction of the aspirated fat is processed for isolation of ASCs, which are then recombined with the remainder of the aspirated fat prior to grafting.¹¹ However, there is conflicting evidence as to whether CAL leads to improved graft success relative to conventional autologous fat transfer.^12,13

The skin also serves as an easily accessible and abundant autologous source of stem cells. A subtype of dermal fibroblasts has been proven to have multipotent potential.^14,15 These dermal fibroblasts are harvested from one area of the skin using punch biopsy and are processed and reinjected into another desired area of the skin.¹⁶ Autologous human fibroblasts have proven to be effective for the treatment of wrinkles, rhytides, and acne scars.¹⁷ In June 2011, the US Food and Drug Administration approved azficel-T, an autologous cellular product created by harvesting fibroblasts from a patient’s own postauricular skin, culture-expanding them in vitro for 3 months, and reinjecting the cells into the desired area of dermis in a series of treatments. This product was the first personalized cell therapy approved by the US Food and Drug Administration for aesthetic uses, specifically for the improvement of nasolabial fold wrinkles.¹⁸

In adults, hair follicles contain an area known as the bulge, which is a site rich in epithelial and melanocytic stem cells. Bulge stem cells have the ability to reproduce the interfollicular epidermis, hair follicle structures, and sebaceous glands, and they have been used to construct entirely new hair follicles in an artificial in vivo system.¹⁹ Sugiyama-Nakagiri et al²⁰ demonstrated that an entire hair follicle epithelium and interfollicular epidermis can be regenerated using cultured bulge stem cells. The cultured bulge stem cells were mixed with dermal papilla cells from neonatal rat vibrissae and engrafted into a silicone chamber implanted on the backs of severe combined immune deficient (SCID) mice. The grafts exhibited tufts of hair as well as a complete interfollicular epidermis at 4 weeks after transplantation.²⁰ Thus, these bulge stem cells have the potential to treat male androgenic alopecia and female pattern hair loss. Bulge stem cells also have been shown to accelerate wound healing.²¹ Additionally, autologous melanocytic stem cells located at the hair follicle bulge are effective for treating vitiligo and are being investigated for the treatment of hair graying.²²

Induced Pluripotent Stem Cells

Given the ethical concerns that surround the procurement and use of embryonic stem cells, efforts have been made to retrieve pluripotent stem cells from adults. A major breakthrough occurred in 2006 when researchers altered the genes of specialized adult mouse cells to cause dedifferentiation and the return to an embryoniclike stem cell state.²³ Mouse somatic cells were reprogrammed through the activation of a combination of transcription factors. The resulting cells were termed induced pluripotent stem cells (iPSCs) and have since been recreated in human cell lines. The discovery of iPSCs precipitated a translational science revolution. Physician-scientists sought ways to apply the reprogrammed cells to the pathophysiology of obscure diseases, examination of drug targets, and regeneration of human tissue.²⁴ Tissue regeneration via induced naïve somatic cells has shown promise as a future method to treat neurologic, cardiovascular, and ophthalmologic diseases.²⁵

As the technology of cultivating and identifying optimal sources of iPSCs continues to advance, stem cell–based treatments have evolved as leading prospects in the field of biogerontology.^26-29 Although much of the research in antiaging medicine has utilized iPSCs to reprogram cell senescence, the altering of iPSCs at a cellular level also allows for the stimulation of collagen synthesis. This potential for collagen generation may have direct applicability in dermatologic practice, particularly for aesthetic treatments.

Much of the research into iPSC-derived collagen has focused on genodermatoses. Itoh et al³⁰ examined the creation of collagen through iPSCs to identify possible treatments for recessive dystrophic epidermolysis bullosa (DEB). Recessive DEB is characterized by mutations in the COL7A1 gene, which encodes type VII collagen, a basement membrane protein and component of the anchoring fibrils essential for skin integrity.³¹ Itoh et al³⁰ began with source cells obtained from a skin biopsy. The cells were dedifferentiated to iPSCs and then induced into dermal fibroblasts according to the methods established in prior studies of embryonic stem cells, namely with the use of ascorbic acid and transforming growth factor b. The newly formed fibroblasts were determined to be functional based on their ability to synthesize mature type VII collagen.³⁰ Once the viability of the iPSC-derived fibroblasts was confirmed in vitro, the cells were further tested through combination with human keratinocytes on SCID mice. The human keratinocytes grew together with the iPSC-derived fibroblasts, producing type VII collagen in the basement membrane zone and creating an epidermis with the normal markers.³⁰ Similarly, Robbins et al³² utilized SCID mice to successfully demonstrate that the transfection of keratinocytes from patients with junctional epidermolysis bullosa into SCID mice produced phenotypically normal skin.

Sebastiano et al³³ combined the concepts of iPSCs and genome editing in another study of recessive DEB. The investigators first cultured iPSCs from biopsies of affected patients. After deriving iPSCs and correcting their mutation via adenovirus-associated viral gene editing, the COL7A1 mutation-free cells were differentiated into keratinocytes. These iPSC-derived keratinocytes were subsequently grafted onto mice, which led to the production of wild-type collagen VII and a stratified epidermis. Despite this successful outcome, the grafts of iPSC-derived epidermis did not survive longer than 1 month.³³

One of the many obstacles facing the practical use of stem cells is their successful incorporation into human tissue. A possible solution was uncovered by Zhang et al³⁴ who examined iPSC-derived MSCs. Mesenchymal stem cells communicate via paracrine mechanisms, whereby exosomes containing RNA and proteins are released to potentiate a regenerative effect.³⁵ Zhang et al³⁴ found that injecting exosomes from human iPSC-derived MSCs into the wound sites of rats stimulated the production of type I collagen, type III collagen, and elastin. The wound sites demonstrated accelerated closure, narrower scar widths, and increased collagen maturity.

Understanding the role that local environment plays in stem cell differentiation, Xu et al³⁶ aimed to create an extracellular scaffold to induce fibroblast behavior from iPSCs. The authors engineered a framework similar to the normal extracellular membrane using proteoglycans, glycosaminoglycans, fibrinogen, and connective tissue growth factor. The iPSCs were then applied to the scaffolding, which led to successful fibroblast differentiation and type I collagen synthesis.³⁶ This use of local biosignaling cues holds important ramifications for controlling the fate of stem cells that have been introduced into a new environment.

Although the application of iPSCs in clinical dermatology has yet to be achieved, progress in the field is moving at a rapid pace. Several logistical elements require further mastery before therapeutics can be delivered. These areas include the optimal environment for iPSC differentiation, methods for maximization of graft survival, and different modes of transplanting iPSC-derived cells into patients. In cosmetic practice, success will depend on intradermal injections of collagen-producing iPSC-derived cells that possess long-term proliferative potential. Current research in mice models has demonstrated viability up to 16 weeks after intradermal injection of such cells.³⁷

Plant Stem Cells

In discussing the dermatologic applications of stem cell technology, clinicians should be aware of the plant stem cell products that have become a popular cosmeceutical trend. Companies advertise plant cells as a natural source of regenerative cells that can induce rejuvenation in human skin; however, there are no significant data to indicate that plant stem cells encourage or activate cellular growth in humans. Indeed, for stem cells to differentiate and produce viable components, the cells must first be incorporated as living components in the host tissue. Because plant stem cells do not survive in human tissue and plant cell cytokines fail to interact with the receptors on human cells, their current value in cosmeceuticals may be overstated.

Platelet-Rich Plasma

Platelet-rich plasma also is commonly associated with stem cell therapy, as PRP is known to potentiate stem cell proliferation, migration, and differentiation. However, PRP does not contain stem cells and is instead autologous plasma concentrated with platelets. In fact, platelets cannot even be classified as cells given that they lack a nucleus; platelets are considered cell fragments. The regenerative potential of PRP can be attributed to the growth factors released from platelets, which play an important role in tissue regeneration and repair. Platelet-rich plasma currently is being used in dermatology for skin rejuvenation (reduction of wrinkles and furrows) and treatment of acne scars.³⁸ There also is evidence supporting the effectiveness of PRP for alopecia and wound therapy, as growth factors play a vital role in hair growth and wound healing.³⁸ Apart from the use of PRP on its own, it can be used as a supplement to enhance the effects of antiaging procedures such as microneedling.³⁹

Future Directions

Multipotent stem cells and iPSCs discussed herein provide much promise in the field of regenerative dermatology. They are increasingly accessible and circumvent the use of ethically questionable embryonic stem cells. Although there is a general consensus on the great potential of stem cells for treating aesthetic skin conditions, high-quality randomized controlled trials remain scarce within the literature. Recognizing and optimizing these opportunities remains the next step in the future delivery of evidence-based care in regenerative dermatology.

Regenerative medicine encompasses innovative therapies that allow the body to repair or regenerate aging cells, tissues, and organs. The skin is a particularly attractive organ for the application of novel regenerative therapies due to its easy accessibility. Among these therapies, stem cells and platelet-rich plasma (PRP) have garnered interest based on their therapeutic potential in scar reduction, antiaging effects, and treatment of alopecia.

Stem cells possess the cardinal features of self-renewal and plasticity. Self-renewal refers to symmetric cell division generating daughter cells identical to the parent cell.¹ Plasticity is the ability to generate cell types other than the germ line or tissue lineage from which stem cells derive.² Stem cells can be categorized according to their differentiation potential. Totipotent stem cells may develop into any primary germ cell layer (ectoderm, mesoderm, endoderm) of the embryo, as well as extraembryonic tissue such as the trophoblast, which gives rise to the placenta. Pluripotent stem cells such as embryonic stem cells have the capacity to differentiate into any derivative of the 3 germ cell layers but have lost their ability to differentiate into the trophoblast.³ Adults lack totipotent or pluripotent cells; they have multipotent or unipotent cells. Multipotent stem cells are able to differentiate into multiple cell types from similar lineages; mesenchymal stem cells (MSCs), for example, can differentiate into adipogenic, osteogenic, chondrogenic, and myogenic cells.⁴ Unipotent stem cells have the lowest differentiation potential and can only self-regenerate. Herein, we review stem cell sources and their therapeutic potential in aesthetic dermatology.

Multipotent Stem Cells

Multipotent stem cells derived from the bone marrow, umbilical cord, adipose tissue, dermis, or hair follicle bulge have various clinical applications in dermatology. Stem cells from these sources are primarily utilized in an autologous manner in which they are processed outside the body and reintroduced into the donor. Autologous multipotent hematopoietic bone marrow cells were first successfully used for the treatment of chronic wounds and show promise for the treatment of atrophic scars.^5,6 However, due to the invasive nature of extracting bone marrow stem cells and their declining number with age, other sources of multipotent stem cells have fallen into favor.

Umbilical cord blood is a source of multipotent hematopoietic stem cells for which surgical intervention is not necessary because they are retrieved after umbilical cord clamping.⁷ Advantages of sourcing stem cells from umbilical cord blood includes high regenerative power compared to a newborn’s skin and low immunogenicity given that the newborn is immunologically immature.⁸

Another popular source for autologous stem cells is adipose tissue due to its ease of accessibility and relative abundance. Given that adipose tissue–derived stem cells (ASCs) are capable of differentiating into adipocytes that help maintain volume over time, they are being used for midface contouring, lip augmentation, facial rejuvenation, facial scarring, lipodystrophy, penile girth enhancement, and vaginal augmentation. Adipose tissue–derived stem cells also are capable of differentiating into other types of tissue, including cartilage and bone. Thus, they have been successfully harnessed in the treatment of patients affected by systemic sclerosis and Parry-Romberg syndrome as well in the functional and aesthetic reconstruction of various military combat–related deformities.^9,10

Adipose tissue–derived stem cells are commonly harvested from lipoaspirate of the abdomen and are combined with supportive mechanical scaffolds such as hydrogels. Lipoaspirate itself can serve as a scaffold for ASCs. Accordingly, ASCs also are being utilized as a scaffold for autologous fat transfer procedures in an effort to increase the viability of transplanted donor tissue, a process known as cell-assisted lipotransfer (CAL). In CAL, a fraction of the aspirated fat is processed for isolation of ASCs, which are then recombined with the remainder of the aspirated fat prior to grafting.¹¹ However, there is conflicting evidence as to whether CAL leads to improved graft success relative to conventional autologous fat transfer.^12,13

The skin also serves as an easily accessible and abundant autologous source of stem cells. A subtype of dermal fibroblasts has been proven to have multipotent potential.^14,15 These dermal fibroblasts are harvested from one area of the skin using punch biopsy and are processed and reinjected into another desired area of the skin.¹⁶ Autologous human fibroblasts have proven to be effective for the treatment of wrinkles, rhytides, and acne scars.¹⁷ In June 2011, the US Food and Drug Administration approved azficel-T, an autologous cellular product created by harvesting fibroblasts from a patient’s own postauricular skin, culture-expanding them in vitro for 3 months, and reinjecting the cells into the desired area of dermis in a series of treatments. This product was the first personalized cell therapy approved by the US Food and Drug Administration for aesthetic uses, specifically for the improvement of nasolabial fold wrinkles.¹⁸

In adults, hair follicles contain an area known as the bulge, which is a site rich in epithelial and melanocytic stem cells. Bulge stem cells have the ability to reproduce the interfollicular epidermis, hair follicle structures, and sebaceous glands, and they have been used to construct entirely new hair follicles in an artificial in vivo system.¹⁹ Sugiyama-Nakagiri et al²⁰ demonstrated that an entire hair follicle epithelium and interfollicular epidermis can be regenerated using cultured bulge stem cells. The cultured bulge stem cells were mixed with dermal papilla cells from neonatal rat vibrissae and engrafted into a silicone chamber implanted on the backs of severe combined immune deficient (SCID) mice. The grafts exhibited tufts of hair as well as a complete interfollicular epidermis at 4 weeks after transplantation.²⁰ Thus, these bulge stem cells have the potential to treat male androgenic alopecia and female pattern hair loss. Bulge stem cells also have been shown to accelerate wound healing.²¹ Additionally, autologous melanocytic stem cells located at the hair follicle bulge are effective for treating vitiligo and are being investigated for the treatment of hair graying.²²

Induced Pluripotent Stem Cells

Given the ethical concerns that surround the procurement and use of embryonic stem cells, efforts have been made to retrieve pluripotent stem cells from adults. A major breakthrough occurred in 2006 when researchers altered the genes of specialized adult mouse cells to cause dedifferentiation and the return to an embryoniclike stem cell state.²³ Mouse somatic cells were reprogrammed through the activation of a combination of transcription factors. The resulting cells were termed induced pluripotent stem cells (iPSCs) and have since been recreated in human cell lines. The discovery of iPSCs precipitated a translational science revolution. Physician-scientists sought ways to apply the reprogrammed cells to the pathophysiology of obscure diseases, examination of drug targets, and regeneration of human tissue.²⁴ Tissue regeneration via induced naïve somatic cells has shown promise as a future method to treat neurologic, cardiovascular, and ophthalmologic diseases.²⁵

As the technology of cultivating and identifying optimal sources of iPSCs continues to advance, stem cell–based treatments have evolved as leading prospects in the field of biogerontology.^26-29 Although much of the research in antiaging medicine has utilized iPSCs to reprogram cell senescence, the altering of iPSCs at a cellular level also allows for the stimulation of collagen synthesis. This potential for collagen generation may have direct applicability in dermatologic practice, particularly for aesthetic treatments.

Much of the research into iPSC-derived collagen has focused on genodermatoses. Itoh et al³⁰ examined the creation of collagen through iPSCs to identify possible treatments for recessive dystrophic epidermolysis bullosa (DEB). Recessive DEB is characterized by mutations in the COL7A1 gene, which encodes type VII collagen, a basement membrane protein and component of the anchoring fibrils essential for skin integrity.³¹ Itoh et al³⁰ began with source cells obtained from a skin biopsy. The cells were dedifferentiated to iPSCs and then induced into dermal fibroblasts according to the methods established in prior studies of embryonic stem cells, namely with the use of ascorbic acid and transforming growth factor b. The newly formed fibroblasts were determined to be functional based on their ability to synthesize mature type VII collagen.³⁰ Once the viability of the iPSC-derived fibroblasts was confirmed in vitro, the cells were further tested through combination with human keratinocytes on SCID mice. The human keratinocytes grew together with the iPSC-derived fibroblasts, producing type VII collagen in the basement membrane zone and creating an epidermis with the normal markers.³⁰ Similarly, Robbins et al³² utilized SCID mice to successfully demonstrate that the transfection of keratinocytes from patients with junctional epidermolysis bullosa into SCID mice produced phenotypically normal skin.

Sebastiano et al³³ combined the concepts of iPSCs and genome editing in another study of recessive DEB. The investigators first cultured iPSCs from biopsies of affected patients. After deriving iPSCs and correcting their mutation via adenovirus-associated viral gene editing, the COL7A1 mutation-free cells were differentiated into keratinocytes. These iPSC-derived keratinocytes were subsequently grafted onto mice, which led to the production of wild-type collagen VII and a stratified epidermis. Despite this successful outcome, the grafts of iPSC-derived epidermis did not survive longer than 1 month.³³

One of the many obstacles facing the practical use of stem cells is their successful incorporation into human tissue. A possible solution was uncovered by Zhang et al³⁴ who examined iPSC-derived MSCs. Mesenchymal stem cells communicate via paracrine mechanisms, whereby exosomes containing RNA and proteins are released to potentiate a regenerative effect.³⁵ Zhang et al³⁴ found that injecting exosomes from human iPSC-derived MSCs into the wound sites of rats stimulated the production of type I collagen, type III collagen, and elastin. The wound sites demonstrated accelerated closure, narrower scar widths, and increased collagen maturity.

Understanding the role that local environment plays in stem cell differentiation, Xu et al³⁶ aimed to create an extracellular scaffold to induce fibroblast behavior from iPSCs. The authors engineered a framework similar to the normal extracellular membrane using proteoglycans, glycosaminoglycans, fibrinogen, and connective tissue growth factor. The iPSCs were then applied to the scaffolding, which led to successful fibroblast differentiation and type I collagen synthesis.³⁶ This use of local biosignaling cues holds important ramifications for controlling the fate of stem cells that have been introduced into a new environment.

Although the application of iPSCs in clinical dermatology has yet to be achieved, progress in the field is moving at a rapid pace. Several logistical elements require further mastery before therapeutics can be delivered. These areas include the optimal environment for iPSC differentiation, methods for maximization of graft survival, and different modes of transplanting iPSC-derived cells into patients. In cosmetic practice, success will depend on intradermal injections of collagen-producing iPSC-derived cells that possess long-term proliferative potential. Current research in mice models has demonstrated viability up to 16 weeks after intradermal injection of such cells.³⁷

Plant Stem Cells

In discussing the dermatologic applications of stem cell technology, clinicians should be aware of the plant stem cell products that have become a popular cosmeceutical trend. Companies advertise plant cells as a natural source of regenerative cells that can induce rejuvenation in human skin; however, there are no significant data to indicate that plant stem cells encourage or activate cellular growth in humans. Indeed, for stem cells to differentiate and produce viable components, the cells must first be incorporated as living components in the host tissue. Because plant stem cells do not survive in human tissue and plant cell cytokines fail to interact with the receptors on human cells, their current value in cosmeceuticals may be overstated.

Platelet-Rich Plasma

Platelet-rich plasma also is commonly associated with stem cell therapy, as PRP is known to potentiate stem cell proliferation, migration, and differentiation. However, PRP does not contain stem cells and is instead autologous plasma concentrated with platelets. In fact, platelets cannot even be classified as cells given that they lack a nucleus; platelets are considered cell fragments. The regenerative potential of PRP can be attributed to the growth factors released from platelets, which play an important role in tissue regeneration and repair. Platelet-rich plasma currently is being used in dermatology for skin rejuvenation (reduction of wrinkles and furrows) and treatment of acne scars.³⁸ There also is evidence supporting the effectiveness of PRP for alopecia and wound therapy, as growth factors play a vital role in hair growth and wound healing.³⁸ Apart from the use of PRP on its own, it can be used as a supplement to enhance the effects of antiaging procedures such as microneedling.³⁹

Future Directions

Multipotent stem cells and iPSCs discussed herein provide much promise in the field of regenerative dermatology. They are increasingly accessible and circumvent the use of ethically questionable embryonic stem cells. Although there is a general consensus on the great potential of stem cells for treating aesthetic skin conditions, high-quality randomized controlled trials remain scarce within the literature. Recognizing and optimizing these opportunities remains the next step in the future delivery of evidence-based care in regenerative dermatology.

Background and Distribution

The Dermacentor ticks belong to the family Ixodidae (hard ticks). The 2 best-known ticks of the genus are Dermacentor andersoni (Rocky Mountain wood tick)(Figure, A) and Dermacentor variabilis (American dog tick)(Figure, B). The Dermacentor ticks are large ticks with small anterior mouthparts that attach to a rectangular basis capituli (Figure, A). Both ticks exhibit widely spaced eyes and posterior festoons as well as bifid coxa 1 (the attachment site for the first pair of legs) and enlarged coxa 4. As adults, these ticks display an ornate hard dorsal plate, or scutum, with numerous pits. Female ticks have a much smaller scutum, allowing for abdominal engorgement during feeding.¹ Although D andersoni tends to have a brown to yellow hue, the specimens of D variabilis display a somewhat silver color pattern.

Dermacentor ticks can be found throughout most of North America, with the northern distribution limits of both species previously occurring in the province of Saskatchewan, Canada. Although the range of D andersoni has remained relatively stable within this distribution, the distribution of D variabilis recently has expanded westward and northward of these limits.² The ranges of the 2 species overlap in certain areas, though D andersoni primarily is found in the Rocky Mountain and northwestern states as well as southwestern Canada, whereas D variabilis can be found throughout most parts of the United States, except in the Rocky Mountain states.³ Within these regions the ticks can be found in heavily wooded areas, but they most commonly inhabit fields with tall grass, crops, bushes, and shrubbery, often clustering where these types of vegetation form clearly defined edges.⁴ The diseases transmitted by the Dermacentor ticks include Rocky Mountain spotted fever (RMSF), Colorado tick fever, tularemia, tick paralysis, and even human monocytic erlichiosis, though Amblyomma americanum is the major vector for human monocytic erlichiosis.

Rocky Mountain Spotted Fever

Both species of ticks are known to serve as vectors for RMSF, but D variabilis is the major vector in the United States, especially in the eastern and southeastern parts of the United States. Overall, the majority of cases occur in North Carolina, South Carolina, Tennessee, and Oklahoma,⁵ with North Carolina having the highest incidence. In endemic areas, RMSF should be suspected in any patient with fever and headache, and empiric treatment with antibiotics should be started while awaiting the results of diagnostic tests. Serologic testing with indirect fluorescent antibodies is widely available and is considered the best method for detection; although the sensitivity is poor during the first 10 to 12 days of infection, it increases to 94% during days 14 to 21.⁶ Therapeutic decisions should be influenced by clinical suspicion and epidemiologic data. Treatment should be started promptly and should never be delayed until confirmatory tests are available. Doxycycline is considered the gold standard therapy in both adults and children, with a typical treatment duration of 10 days. The only other recommended agent for pregnant women in the first or second trimesters or patients with severe hypersensitivity reactions to tetracyclines is chloramphenicol.⁷

Colorado Tick Fever

Colorado tick fever, also known as mountain fever, is an arboviral infection transmitted by D andersoni. Its distribution coincides with the tick’s natural geographic range in the western United States and Rocky Mountains. Colorado tick fever causes an acute febrile illness consisting of chills, headaches, myalgia, retro-orbital pain, and malaise, which tend to occur within 3 to 5 days of the tick bite. Some cases may be accompanied by a nonspecific rash that may be morbilliform or petechial in appearance. Notably, approximately half of all patients will experience transient resolution of symptoms for 24 to 48 hours followed by a recurrence of fever, a phenomenon that has been referred to as saddleback fever. Routine laboratory findings may include leukopenia, thrombocytopenia, and a peripheral smear with atypical lymphocytes. Reverse transcription polymerase chain reaction is both sensitive and specific for detecting viral loads in the blood during the first week of infection, though testing does not alter management, which is largely supportive.⁸

Tularemia

Tularemia is a relatively rare disease but has been documented in every US state except Hawaii.⁹ The disease is caused by Francisella tularensis, a small, aerobic, gram-negative coccobacillus transmitted via inhalation, bitingflies, or tick bites; the most common ticks to transmit the disease include D andersoni, D variabilis, and A americanum.¹⁰ Clinical manifestations depend on the form of exposure, with tick bites most often resulting in an ulcerated skin lesion at the site of the vector bite accompanied by regional lymphadenopathy and systemic symptoms such as fever, chills, myalgia, and headache.¹¹ Mucosal manifestations such as pharyngitis, conjunctivitis, and other ocular lesions also are commonly seen. Diagnosis most frequently is made using serology because F tularensis is both challenging and dangerous to culture; in fact, because of the high risk of contagion, F tularensis should only be cultured in biosafety level 3 laboratories. Polymerase chain reaction assays can be used on tissue samples with decent sensitivity (78%) and specificity (96%); however, these assays cannot distinguish between Francisella subspecies and are not readily available to most clinicians.¹² First-line therapy for the treatment of tularemia is streptomycin given as twice-daily intramuscular injections over the course of 7 to 10 days. Alternative agents include gentamicin, ciprofloxacin, imipenem, doxycycline, and chloramphenicol.¹⁰ Because tularemia is relatively rare, a high index of suspicion is necessary to reduce the morbidity and mortality associated with the disease.

Tick Paralysis

More than 40 different species of ticks have been implicated worldwide as causes of tick paralysis, though D andersoni has been the most common in North America. Female patients account for most cases, possibly because long hair conceals ticks on the scalp or neck, the preferred attachment locations for Dermacentor ticks.¹³ The classic presentation of tick paralysis is an acute, flaccid, ascending paralysis that occurs from a neurotoxin in the tick saliva that impairs afferent nerve signal propagation.^14,15 The paralysis progresses over hours to days and typically occurs 5 to 6 days after attachment of the tick. Notably, there is no associated fever with tick paralysis, and without intervention, patients may die of respiratory failure. Overall, the condition carries a fatality rate of nearly 10%¹⁶ but reverses rapidly if the tick is identified and removed.

Protection against tick bites and tick-borne illnesses includes avoidance of infested areas, treatment of populated habitats with insecticide sprays, use of topical repellants prior to outdoor activities, and diligent full-body tick checks upon return from tick-heavy areas. Permethrin can be used to treat clothing and remains protective through multiple washings. Ticks typically survive washing of untreated clothing but are killed by prolonged drying in a dryer. Pets may be treated with oral, intramuscular, or topical agents prescribed by a veterinarian to prevent tick attachments.

Conclusion

Accurate identification of Dermacentor ticks allows for appropriate surveillance for associated diseases and can improve patient outcomes. Patients who engage in outdoor activities in endemic areas should take steps to avoid exposure, use appropriate acaricides and repellents, and perform tick checks after returning indoors.

Background and Distribution

The Dermacentor ticks belong to the family Ixodidae (hard ticks). The 2 best-known ticks of the genus are Dermacentor andersoni (Rocky Mountain wood tick)(Figure, A) and Dermacentor variabilis (American dog tick)(Figure, B). The Dermacentor ticks are large ticks with small anterior mouthparts that attach to a rectangular basis capituli (Figure, A). Both ticks exhibit widely spaced eyes and posterior festoons as well as bifid coxa 1 (the attachment site for the first pair of legs) and enlarged coxa 4. As adults, these ticks display an ornate hard dorsal plate, or scutum, with numerous pits. Female ticks have a much smaller scutum, allowing for abdominal engorgement during feeding.¹ Although D andersoni tends to have a brown to yellow hue, the specimens of D variabilis display a somewhat silver color pattern.

Dermacentor ticks can be found throughout most of North America, with the northern distribution limits of both species previously occurring in the province of Saskatchewan, Canada. Although the range of D andersoni has remained relatively stable within this distribution, the distribution of D variabilis recently has expanded westward and northward of these limits.² The ranges of the 2 species overlap in certain areas, though D andersoni primarily is found in the Rocky Mountain and northwestern states as well as southwestern Canada, whereas D variabilis can be found throughout most parts of the United States, except in the Rocky Mountain states.³ Within these regions the ticks can be found in heavily wooded areas, but they most commonly inhabit fields with tall grass, crops, bushes, and shrubbery, often clustering where these types of vegetation form clearly defined edges.⁴ The diseases transmitted by the Dermacentor ticks include Rocky Mountain spotted fever (RMSF), Colorado tick fever, tularemia, tick paralysis, and even human monocytic erlichiosis, though Amblyomma americanum is the major vector for human monocytic erlichiosis.

Rocky Mountain Spotted Fever

Both species of ticks are known to serve as vectors for RMSF, but D variabilis is the major vector in the United States, especially in the eastern and southeastern parts of the United States. Overall, the majority of cases occur in North Carolina, South Carolina, Tennessee, and Oklahoma,⁵ with North Carolina having the highest incidence. In endemic areas, RMSF should be suspected in any patient with fever and headache, and empiric treatment with antibiotics should be started while awaiting the results of diagnostic tests. Serologic testing with indirect fluorescent antibodies is widely available and is considered the best method for detection; although the sensitivity is poor during the first 10 to 12 days of infection, it increases to 94% during days 14 to 21.⁶ Therapeutic decisions should be influenced by clinical suspicion and epidemiologic data. Treatment should be started promptly and should never be delayed until confirmatory tests are available. Doxycycline is considered the gold standard therapy in both adults and children, with a typical treatment duration of 10 days. The only other recommended agent for pregnant women in the first or second trimesters or patients with severe hypersensitivity reactions to tetracyclines is chloramphenicol.⁷

Colorado Tick Fever

Colorado tick fever, also known as mountain fever, is an arboviral infection transmitted by D andersoni. Its distribution coincides with the tick’s natural geographic range in the western United States and Rocky Mountains. Colorado tick fever causes an acute febrile illness consisting of chills, headaches, myalgia, retro-orbital pain, and malaise, which tend to occur within 3 to 5 days of the tick bite. Some cases may be accompanied by a nonspecific rash that may be morbilliform or petechial in appearance. Notably, approximately half of all patients will experience transient resolution of symptoms for 24 to 48 hours followed by a recurrence of fever, a phenomenon that has been referred to as saddleback fever. Routine laboratory findings may include leukopenia, thrombocytopenia, and a peripheral smear with atypical lymphocytes. Reverse transcription polymerase chain reaction is both sensitive and specific for detecting viral loads in the blood during the first week of infection, though testing does not alter management, which is largely supportive.⁸

Tularemia

Tularemia is a relatively rare disease but has been documented in every US state except Hawaii.⁹ The disease is caused by Francisella tularensis, a small, aerobic, gram-negative coccobacillus transmitted via inhalation, bitingflies, or tick bites; the most common ticks to transmit the disease include D andersoni, D variabilis, and A americanum.¹⁰ Clinical manifestations depend on the form of exposure, with tick bites most often resulting in an ulcerated skin lesion at the site of the vector bite accompanied by regional lymphadenopathy and systemic symptoms such as fever, chills, myalgia, and headache.¹¹ Mucosal manifestations such as pharyngitis, conjunctivitis, and other ocular lesions also are commonly seen. Diagnosis most frequently is made using serology because F tularensis is both challenging and dangerous to culture; in fact, because of the high risk of contagion, F tularensis should only be cultured in biosafety level 3 laboratories. Polymerase chain reaction assays can be used on tissue samples with decent sensitivity (78%) and specificity (96%); however, these assays cannot distinguish between Francisella subspecies and are not readily available to most clinicians.¹² First-line therapy for the treatment of tularemia is streptomycin given as twice-daily intramuscular injections over the course of 7 to 10 days. Alternative agents include gentamicin, ciprofloxacin, imipenem, doxycycline, and chloramphenicol.¹⁰ Because tularemia is relatively rare, a high index of suspicion is necessary to reduce the morbidity and mortality associated with the disease.

Tick Paralysis

More than 40 different species of ticks have been implicated worldwide as causes of tick paralysis, though D andersoni has been the most common in North America. Female patients account for most cases, possibly because long hair conceals ticks on the scalp or neck, the preferred attachment locations for Dermacentor ticks.¹³ The classic presentation of tick paralysis is an acute, flaccid, ascending paralysis that occurs from a neurotoxin in the tick saliva that impairs afferent nerve signal propagation.^14,15 The paralysis progresses over hours to days and typically occurs 5 to 6 days after attachment of the tick. Notably, there is no associated fever with tick paralysis, and without intervention, patients may die of respiratory failure. Overall, the condition carries a fatality rate of nearly 10%¹⁶ but reverses rapidly if the tick is identified and removed.

Protection against tick bites and tick-borne illnesses includes avoidance of infested areas, treatment of populated habitats with insecticide sprays, use of topical repellants prior to outdoor activities, and diligent full-body tick checks upon return from tick-heavy areas. Permethrin can be used to treat clothing and remains protective through multiple washings. Ticks typically survive washing of untreated clothing but are killed by prolonged drying in a dryer. Pets may be treated with oral, intramuscular, or topical agents prescribed by a veterinarian to prevent tick attachments.

Conclusion

Accurate identification of Dermacentor ticks allows for appropriate surveillance for associated diseases and can improve patient outcomes. Patients who engage in outdoor activities in endemic areas should take steps to avoid exposure, use appropriate acaricides and repellents, and perform tick checks after returning indoors.

Background and Distribution

The Dermacentor ticks belong to the family Ixodidae (hard ticks). The 2 best-known ticks of the genus are Dermacentor andersoni (Rocky Mountain wood tick)(Figure, A) and Dermacentor variabilis (American dog tick)(Figure, B). The Dermacentor ticks are large ticks with small anterior mouthparts that attach to a rectangular basis capituli (Figure, A). Both ticks exhibit widely spaced eyes and posterior festoons as well as bifid coxa 1 (the attachment site for the first pair of legs) and enlarged coxa 4. As adults, these ticks display an ornate hard dorsal plate, or scutum, with numerous pits. Female ticks have a much smaller scutum, allowing for abdominal engorgement during feeding.¹ Although D andersoni tends to have a brown to yellow hue, the specimens of D variabilis display a somewhat silver color pattern.

Dermacentor ticks can be found throughout most of North America, with the northern distribution limits of both species previously occurring in the province of Saskatchewan, Canada. Although the range of D andersoni has remained relatively stable within this distribution, the distribution of D variabilis recently has expanded westward and northward of these limits.² The ranges of the 2 species overlap in certain areas, though D andersoni primarily is found in the Rocky Mountain and northwestern states as well as southwestern Canada, whereas D variabilis can be found throughout most parts of the United States, except in the Rocky Mountain states.³ Within these regions the ticks can be found in heavily wooded areas, but they most commonly inhabit fields with tall grass, crops, bushes, and shrubbery, often clustering where these types of vegetation form clearly defined edges.⁴ The diseases transmitted by the Dermacentor ticks include Rocky Mountain spotted fever (RMSF), Colorado tick fever, tularemia, tick paralysis, and even human monocytic erlichiosis, though Amblyomma americanum is the major vector for human monocytic erlichiosis.

Rocky Mountain Spotted Fever

Both species of ticks are known to serve as vectors for RMSF, but D variabilis is the major vector in the United States, especially in the eastern and southeastern parts of the United States. Overall, the majority of cases occur in North Carolina, South Carolina, Tennessee, and Oklahoma,⁵ with North Carolina having the highest incidence. In endemic areas, RMSF should be suspected in any patient with fever and headache, and empiric treatment with antibiotics should be started while awaiting the results of diagnostic tests. Serologic testing with indirect fluorescent antibodies is widely available and is considered the best method for detection; although the sensitivity is poor during the first 10 to 12 days of infection, it increases to 94% during days 14 to 21.⁶ Therapeutic decisions should be influenced by clinical suspicion and epidemiologic data. Treatment should be started promptly and should never be delayed until confirmatory tests are available. Doxycycline is considered the gold standard therapy in both adults and children, with a typical treatment duration of 10 days. The only other recommended agent for pregnant women in the first or second trimesters or patients with severe hypersensitivity reactions to tetracyclines is chloramphenicol.⁷

Colorado Tick Fever

Colorado tick fever, also known as mountain fever, is an arboviral infection transmitted by D andersoni. Its distribution coincides with the tick’s natural geographic range in the western United States and Rocky Mountains. Colorado tick fever causes an acute febrile illness consisting of chills, headaches, myalgia, retro-orbital pain, and malaise, which tend to occur within 3 to 5 days of the tick bite. Some cases may be accompanied by a nonspecific rash that may be morbilliform or petechial in appearance. Notably, approximately half of all patients will experience transient resolution of symptoms for 24 to 48 hours followed by a recurrence of fever, a phenomenon that has been referred to as saddleback fever. Routine laboratory findings may include leukopenia, thrombocytopenia, and a peripheral smear with atypical lymphocytes. Reverse transcription polymerase chain reaction is both sensitive and specific for detecting viral loads in the blood during the first week of infection, though testing does not alter management, which is largely supportive.⁸

Tularemia

Tularemia is a relatively rare disease but has been documented in every US state except Hawaii.⁹ The disease is caused by Francisella tularensis, a small, aerobic, gram-negative coccobacillus transmitted via inhalation, bitingflies, or tick bites; the most common ticks to transmit the disease include D andersoni, D variabilis, and A americanum.¹⁰ Clinical manifestations depend on the form of exposure, with tick bites most often resulting in an ulcerated skin lesion at the site of the vector bite accompanied by regional lymphadenopathy and systemic symptoms such as fever, chills, myalgia, and headache.¹¹ Mucosal manifestations such as pharyngitis, conjunctivitis, and other ocular lesions also are commonly seen. Diagnosis most frequently is made using serology because F tularensis is both challenging and dangerous to culture; in fact, because of the high risk of contagion, F tularensis should only be cultured in biosafety level 3 laboratories. Polymerase chain reaction assays can be used on tissue samples with decent sensitivity (78%) and specificity (96%); however, these assays cannot distinguish between Francisella subspecies and are not readily available to most clinicians.¹² First-line therapy for the treatment of tularemia is streptomycin given as twice-daily intramuscular injections over the course of 7 to 10 days. Alternative agents include gentamicin, ciprofloxacin, imipenem, doxycycline, and chloramphenicol.¹⁰ Because tularemia is relatively rare, a high index of suspicion is necessary to reduce the morbidity and mortality associated with the disease.

Tick Paralysis

More than 40 different species of ticks have been implicated worldwide as causes of tick paralysis, though D andersoni has been the most common in North America. Female patients account for most cases, possibly because long hair conceals ticks on the scalp or neck, the preferred attachment locations for Dermacentor ticks.¹³ The classic presentation of tick paralysis is an acute, flaccid, ascending paralysis that occurs from a neurotoxin in the tick saliva that impairs afferent nerve signal propagation.^14,15 The paralysis progresses over hours to days and typically occurs 5 to 6 days after attachment of the tick. Notably, there is no associated fever with tick paralysis, and without intervention, patients may die of respiratory failure. Overall, the condition carries a fatality rate of nearly 10%¹⁶ but reverses rapidly if the tick is identified and removed.

Protection against tick bites and tick-borne illnesses includes avoidance of infested areas, treatment of populated habitats with insecticide sprays, use of topical repellants prior to outdoor activities, and diligent full-body tick checks upon return from tick-heavy areas. Permethrin can be used to treat clothing and remains protective through multiple washings. Ticks typically survive washing of untreated clothing but are killed by prolonged drying in a dryer. Pets may be treated with oral, intramuscular, or topical agents prescribed by a veterinarian to prevent tick attachments.

Conclusion

Accurate identification of Dermacentor ticks allows for appropriate surveillance for associated diseases and can improve patient outcomes. Patients who engage in outdoor activities in endemic areas should take steps to avoid exposure, use appropriate acaricides and repellents, and perform tick checks after returning indoors.

The prevalence of psoriasis among human immunodeficiency virus (HIV)–positive patients in the United States is reported to be approximately 1% to 3%, which is similar to the rates reported for the general population.¹ Recalcitrant cases of psoriasis in patients with no history of the condition can be the initial manifestation of HIV infection. In patients with preexisting psoriasis, a flare of their disease can be seen following infection, and progression of HIV correlates with worsening psoriasis.² Psoriatic arthropathy also affects 23% to 50% of HIV-positive patients with psoriasis worldwide, which may be higher than the general population,¹ with more severe joint disease.

The management of psoriatic disease in the HIV-positive population is challenging. The current first-line recommendations for treatment include topical therapies, phototherapy, and highly active antiretroviral therapy (HAART), followed by oral retinoids as second-line agents.³ However, the clinical course of psoriasis in HIV-positive patients often is progressive and refractory²; therefore, these therapies often are inadequate to control both skin and joint manifestations. Most other currently available systemic therapies for psoriatic disease are immunosuppressive, which poses a distinct clinical challenge because HIV-positive patients are already immunocompromised.

There currently are many systemic immunosuppressive agents used for the treatment of psoriatic disease, including oral agents (eg, methotrexate, hydroxyurea, cyclosporine), as well as newer biologic medications, including tumor necrosis factor (TNF) α inhibitors etanercept, adalimumab, infliximab, golimumab, and certolizumab pegol. Golimumab and certolizumab pegol currently are indicated for psoriatic arthritis only. Other newer biologic therapies include ustekinumab, which inhibits IL-12 and IL-23, and secukinumab, which inhibits IL-17A. The purpose of this systematic review is to evaluate the most current literature to explore the efficacy and safety data as they pertain to systemic immunosuppressive therapies for the treatment of psoriatic disease in HIV-positive individuals.

Methods

To investigate the efficacy and safety of systemic immunosuppressive therapies for psoriatic disease in HIV-positive individuals, a PubMed search of articles indexed for MEDLINE (1985-2015) was conducted using the terms psoriasis and HIV and psoriatic arthritis and HIV combined with each of the following systemic immunosuppressive agents: methotrexate, hydroxyurea, cyclosporine, etanercept, adalimumab, infliximab, golimumab, certolizumab pegol, ustekinumab, and secukinumab. Pediatric cases and articles that were not available in the English language were excluded.

For each case, patient demographic information (ie, age, sex), prior failed psoriasis treatments, and history of HAART were documented. The dosing regimen of the systemic agent was noted when different from the US Food and Drug administration–approved dosage for psoriasis or psoriatic arthritis. The duration of immunosuppressive therapy as well as pretreatment and posttreatment CD4 and viral counts (when available) were collected. The response to treatment and adverse effects were summarized.

Results

Our review of the literature yielded a total of 25 reported cases of systemic immunosuppressive therapies used to treat psoriatic disease in HIV-positive patients, including methotrexate, cyclosporine, etanercept, adalimumab, in-fliximab, and ustekinumab (Table). There were no reports of the use of hydroxyurea, golimumab, certolizumab pegol, or secukinumab to treat psoriatic disease in this patient population.

Methotrexate
Eight individual cases of methotrexate used to treat psoriasis and/or psoriatic arthritis in HIV-positive patients were reported.^4-6 Duvic et al⁶ described 4 patients with psoriatic disease that was treated with methotrexate with varying efficacy. One patient developed toxic encephalopathy, which improved after discontinuation of methotrexate; however, he died 5 months later from pneumocystis pneumonia. In this early study, none of the 4 patients were on antiretroviral therapy for HIV.⁶

In the cases reported by Masson et al⁴ and Maurer et al,⁵ 4 patients were treated with a single antiretroviral agent and received appropriate prophylaxis against opportunistic infections. In 1 case, methotrexate was given at a chemotherapeutic dose of 525 mg once weekly for Kaposi sarcoma.⁴ In 2 of 4 cases, the patients developed pneumocystis pneumonia.^4,5

Cyclosporine
There were 2 case reports of successful treatment of psoriatic disease with cyclosporine in HIV-positive patients.^7,8 Skin and joint manifestations improved rapidly without reports of infection for 2⁷ and 8 years.⁸ Both patients were treated with one antiretroviral agent.^7,8

Etanercept
There were 5 case reports of successful treatment of psoriatic disease with etanercept. In all 5 cases the patients were on HAART, and the CD4 count increased or remained stable and viral count became undetectable or remained stable following treatment.^9-13 In 2 cases, the patient also had hepatitis C virus, which remained stable throughout the treatment period.^9,12 The maximum duration of treatment was 6 years, with only 1 reported adverse event.¹³ In this case reported by Aboulafia et al,¹³ the patient experienced recurrent polymicrobial infections, including enterococcal cellulitis, cystitis, and bacteremia, as well as pseudomonas pneumonia and septic arthritis. Therapy was discontinued at 6 months. Four months after discontinuation of etanercept, the patient died from infectious causes.¹³

Adalimumab
There was 1 case of successful treatment of psoriatic disease with adalimumab in an HIV-positive patient. In this case, the patient was on HAART, and CD4 and viral counts improved substantially after 30 months of treatment.¹⁴

Infliximab
Six individual cases of successful treatment of psoriatic disease with infliximab were reported.^15-17 In a report by Cepeda et al,¹⁵ HIV-positive patients with various rheumatologic diseases were chosen to receive etanercept followed by adalimumab and/or infliximab if clinical improvement was not observed on etanercept. In 3 patients with psoriasis and psoriatic arthritis, inadequate response was observed on etanercept. Two of these 3 patients received adalimumab with only partial response. All 3 were treated with infliximab in the end and showed excellent response. One of the patients experienced facial abscess responsive to antibiotics and was continued on infliximab therapy without further complications. In all 6 cases of infliximab therapy, the patients were on HAART, and CD4 and viral counts improved or remained stable.¹⁵

Ustekinumab
There were 3 case reports of successful treatment of psoriatic disease with ustekinumab in HIV-positive patients on HAART. CD4 and viral counts improved or remained stable.^18-20

Comment

Currently, all of the systemic immunosuppressive therapies approved for psoriatic disease have a warning by the US Food and Drug Administration for increased risk of serious infection. Given such labels, these therapies are not routinely prescribed for HIV-positive patients who are already immunocompromised; however, many HIV-positive patients have severe psoriatic disease that cannot be adequately treated with first- and second-line therapies including topical agents, phototherapy, or oral retinoids.

Our comprehensive review yielded a total of 25 reported cases of systemic immunosuppressive therapies used to treat psoriatic disease in HIV-positive patients including methotrexate, cyclosporine, etanercept, adalimumab, in-fliximab, and ustekinumab. Although data are limited to case reports and case series, some trends were observed.

Efficacy
In most of the cases reviewed, the patients had inadequate improvement of psoriatic disease with first- and second-line therapies, which included antiretrovirals alone, topical agents, phototherapy, and oral retinoids. Some cases reported poor response to methotrexate and cyclosporine.^4-8 Biologic agents were effective in many such cases.

Safety
Overall, there were 11 cases in which the patient was not on adequate HAART while being treated with systemic immunosuppressive therapy for psoriatic disease.^4-8,15 Of them, 3 were associated with serious infection while on methotrexate.^5,6 There was only 1 report of serious infection¹³ of 14 cases in which the patient was on concomitant HAART. In this case, which reported polymicrobial infections and subsequent death of the patient, the infections continued after discontinuing etanercept; thus, the association is unclear. Interestingly, despite multiple infections, the CD4 and viral counts were stable throughout treatment with etanercept.¹³

From reviewing the 4 total cases^5,6,13 of serious infection, HAART appears to be a valuable concomitant treatment during systemic immunosuppressive therapy for HIV-positive patients; however, it does not necessarily prevent serious infections from occurring, and thus the clinician’s diligence in monitoring for signs and symptoms of infection remains important.

CD4 and Viral Counts
Although reports of CD4 and viral counts were not available in earlier studies,^4-8 there were 15 cases that reported consistent pretreatment and posttreatment CD4 and viral counts during treatment with etanercept, adalimumab, infliximab, and ustekinumab.^9-20 In all cases, the CD4 count was stable or increased. Similarly, the viral count was stable or decreased. All patients, except 1 by Cepeda et al,¹⁵ were on concomitant HAART.^9-14,16-20

Although data are limited, treatment of psoriatic disease with biologic agents when used in combination with HAART may have beneficial effects on CD4 and viral counts. Tumor necrosis factor has a role in HIV expression through the action of nuclear factor κβ.²¹ An increase in TNF levels is shown to be associated with increased viral count, decreased CD4 count, and increased symptoms of HIV progression, such as fever, fatigue, cachexia, and dementia.²² Although more studies are necessary, TNF-α inhibitors may have a positive effect on HIV while simultaneously treating psoriatic disease. Other cytokines (eg, IL-12, IL-23, IL-17) involved in the mechanism of action of other biologic agents (ustekinumab and secukinumab) have not been shown to be directly associated with HIV activity; however, studies have shown that IL-10 has a role in inhibiting HIV-1 replication and inhibits secretion of proinflammatory cytokines such as IL-12 and TNF-α.²¹ It may be speculated that the inhibition of IL-12 and TNF-α may create a positive feedback effect to increase IL-10, which in turn inhibits HIV replication.

Conclusion

Although there are limited data on the efficacy and safety of systemic immunosuppressive therapies for the treatment of psoriatic disease in HIV-positive patients, a review of 25 individual cases suggest that these treatments are not only required but also are sufficient to treat some of the most resistant cases. It is possible that with adequate concomitant HAART and monitoring for signs and symptoms of infection, the likelihood of serious infection may be low. Furthermore, biologic agents may have a positive effect over other systemic immunosuppressive agents, such as methotrexate and cyclosporine, in improving CD4 and viral counts when used in combination with HAART. Although randomized controlled trials are necessary, current biologic therapies such as etanercept, adalimumab, infliximab, and ustekinumab may be safe viable options as third-line treatment of severe psoriasis in the HIV-positive population.

The prevalence of psoriasis among human immunodeficiency virus (HIV)–positive patients in the United States is reported to be approximately 1% to 3%, which is similar to the rates reported for the general population.¹ Recalcitrant cases of psoriasis in patients with no history of the condition can be the initial manifestation of HIV infection. In patients with preexisting psoriasis, a flare of their disease can be seen following infection, and progression of HIV correlates with worsening psoriasis.² Psoriatic arthropathy also affects 23% to 50% of HIV-positive patients with psoriasis worldwide, which may be higher than the general population,¹ with more severe joint disease.

The management of psoriatic disease in the HIV-positive population is challenging. The current first-line recommendations for treatment include topical therapies, phototherapy, and highly active antiretroviral therapy (HAART), followed by oral retinoids as second-line agents.³ However, the clinical course of psoriasis in HIV-positive patients often is progressive and refractory²; therefore, these therapies often are inadequate to control both skin and joint manifestations. Most other currently available systemic therapies for psoriatic disease are immunosuppressive, which poses a distinct clinical challenge because HIV-positive patients are already immunocompromised.

There currently are many systemic immunosuppressive agents used for the treatment of psoriatic disease, including oral agents (eg, methotrexate, hydroxyurea, cyclosporine), as well as newer biologic medications, including tumor necrosis factor (TNF) α inhibitors etanercept, adalimumab, infliximab, golimumab, and certolizumab pegol. Golimumab and certolizumab pegol currently are indicated for psoriatic arthritis only. Other newer biologic therapies include ustekinumab, which inhibits IL-12 and IL-23, and secukinumab, which inhibits IL-17A. The purpose of this systematic review is to evaluate the most current literature to explore the efficacy and safety data as they pertain to systemic immunosuppressive therapies for the treatment of psoriatic disease in HIV-positive individuals.

Methods

To investigate the efficacy and safety of systemic immunosuppressive therapies for psoriatic disease in HIV-positive individuals, a PubMed search of articles indexed for MEDLINE (1985-2015) was conducted using the terms psoriasis and HIV and psoriatic arthritis and HIV combined with each of the following systemic immunosuppressive agents: methotrexate, hydroxyurea, cyclosporine, etanercept, adalimumab, infliximab, golimumab, certolizumab pegol, ustekinumab, and secukinumab. Pediatric cases and articles that were not available in the English language were excluded.

For each case, patient demographic information (ie, age, sex), prior failed psoriasis treatments, and history of HAART were documented. The dosing regimen of the systemic agent was noted when different from the US Food and Drug administration–approved dosage for psoriasis or psoriatic arthritis. The duration of immunosuppressive therapy as well as pretreatment and posttreatment CD4 and viral counts (when available) were collected. The response to treatment and adverse effects were summarized.

Results

Our review of the literature yielded a total of 25 reported cases of systemic immunosuppressive therapies used to treat psoriatic disease in HIV-positive patients, including methotrexate, cyclosporine, etanercept, adalimumab, in-fliximab, and ustekinumab (Table). There were no reports of the use of hydroxyurea, golimumab, certolizumab pegol, or secukinumab to treat psoriatic disease in this patient population.

Methotrexate
Eight individual cases of methotrexate used to treat psoriasis and/or psoriatic arthritis in HIV-positive patients were reported.^4-6 Duvic et al⁶ described 4 patients with psoriatic disease that was treated with methotrexate with varying efficacy. One patient developed toxic encephalopathy, which improved after discontinuation of methotrexate; however, he died 5 months later from pneumocystis pneumonia. In this early study, none of the 4 patients were on antiretroviral therapy for HIV.⁶

In the cases reported by Masson et al⁴ and Maurer et al,⁵ 4 patients were treated with a single antiretroviral agent and received appropriate prophylaxis against opportunistic infections. In 1 case, methotrexate was given at a chemotherapeutic dose of 525 mg once weekly for Kaposi sarcoma.⁴ In 2 of 4 cases, the patients developed pneumocystis pneumonia.^4,5

Cyclosporine
There were 2 case reports of successful treatment of psoriatic disease with cyclosporine in HIV-positive patients.^7,8 Skin and joint manifestations improved rapidly without reports of infection for 2⁷ and 8 years.⁸ Both patients were treated with one antiretroviral agent.^7,8

Etanercept
There were 5 case reports of successful treatment of psoriatic disease with etanercept. In all 5 cases the patients were on HAART, and the CD4 count increased or remained stable and viral count became undetectable or remained stable following treatment.^9-13 In 2 cases, the patient also had hepatitis C virus, which remained stable throughout the treatment period.^9,12 The maximum duration of treatment was 6 years, with only 1 reported adverse event.¹³ In this case reported by Aboulafia et al,¹³ the patient experienced recurrent polymicrobial infections, including enterococcal cellulitis, cystitis, and bacteremia, as well as pseudomonas pneumonia and septic arthritis. Therapy was discontinued at 6 months. Four months after discontinuation of etanercept, the patient died from infectious causes.¹³

Adalimumab
There was 1 case of successful treatment of psoriatic disease with adalimumab in an HIV-positive patient. In this case, the patient was on HAART, and CD4 and viral counts improved substantially after 30 months of treatment.¹⁴

Infliximab
Six individual cases of successful treatment of psoriatic disease with infliximab were reported.^15-17 In a report by Cepeda et al,¹⁵ HIV-positive patients with various rheumatologic diseases were chosen to receive etanercept followed by adalimumab and/or infliximab if clinical improvement was not observed on etanercept. In 3 patients with psoriasis and psoriatic arthritis, inadequate response was observed on etanercept. Two of these 3 patients received adalimumab with only partial response. All 3 were treated with infliximab in the end and showed excellent response. One of the patients experienced facial abscess responsive to antibiotics and was continued on infliximab therapy without further complications. In all 6 cases of infliximab therapy, the patients were on HAART, and CD4 and viral counts improved or remained stable.¹⁵

Ustekinumab
There were 3 case reports of successful treatment of psoriatic disease with ustekinumab in HIV-positive patients on HAART. CD4 and viral counts improved or remained stable.^18-20

Comment

Currently, all of the systemic immunosuppressive therapies approved for psoriatic disease have a warning by the US Food and Drug Administration for increased risk of serious infection. Given such labels, these therapies are not routinely prescribed for HIV-positive patients who are already immunocompromised; however, many HIV-positive patients have severe psoriatic disease that cannot be adequately treated with first- and second-line therapies including topical agents, phototherapy, or oral retinoids.

Our comprehensive review yielded a total of 25 reported cases of systemic immunosuppressive therapies used to treat psoriatic disease in HIV-positive patients including methotrexate, cyclosporine, etanercept, adalimumab, in-fliximab, and ustekinumab. Although data are limited to case reports and case series, some trends were observed.

Efficacy
In most of the cases reviewed, the patients had inadequate improvement of psoriatic disease with first- and second-line therapies, which included antiretrovirals alone, topical agents, phototherapy, and oral retinoids. Some cases reported poor response to methotrexate and cyclosporine.^4-8 Biologic agents were effective in many such cases.

Safety
Overall, there were 11 cases in which the patient was not on adequate HAART while being treated with systemic immunosuppressive therapy for psoriatic disease.^4-8,15 Of them, 3 were associated with serious infection while on methotrexate.^5,6 There was only 1 report of serious infection¹³ of 14 cases in which the patient was on concomitant HAART. In this case, which reported polymicrobial infections and subsequent death of the patient, the infections continued after discontinuing etanercept; thus, the association is unclear. Interestingly, despite multiple infections, the CD4 and viral counts were stable throughout treatment with etanercept.¹³

From reviewing the 4 total cases^5,6,13 of serious infection, HAART appears to be a valuable concomitant treatment during systemic immunosuppressive therapy for HIV-positive patients; however, it does not necessarily prevent serious infections from occurring, and thus the clinician’s diligence in monitoring for signs and symptoms of infection remains important.

CD4 and Viral Counts
Although reports of CD4 and viral counts were not available in earlier studies,^4-8 there were 15 cases that reported consistent pretreatment and posttreatment CD4 and viral counts during treatment with etanercept, adalimumab, infliximab, and ustekinumab.^9-20 In all cases, the CD4 count was stable or increased. Similarly, the viral count was stable or decreased. All patients, except 1 by Cepeda et al,¹⁵ were on concomitant HAART.^9-14,16-20

Although data are limited, treatment of psoriatic disease with biologic agents when used in combination with HAART may have beneficial effects on CD4 and viral counts. Tumor necrosis factor has a role in HIV expression through the action of nuclear factor κβ.²¹ An increase in TNF levels is shown to be associated with increased viral count, decreased CD4 count, and increased symptoms of HIV progression, such as fever, fatigue, cachexia, and dementia.²² Although more studies are necessary, TNF-α inhibitors may have a positive effect on HIV while simultaneously treating psoriatic disease. Other cytokines (eg, IL-12, IL-23, IL-17) involved in the mechanism of action of other biologic agents (ustekinumab and secukinumab) have not been shown to be directly associated with HIV activity; however, studies have shown that IL-10 has a role in inhibiting HIV-1 replication and inhibits secretion of proinflammatory cytokines such as IL-12 and TNF-α.²¹ It may be speculated that the inhibition of IL-12 and TNF-α may create a positive feedback effect to increase IL-10, which in turn inhibits HIV replication.

Conclusion

Although there are limited data on the efficacy and safety of systemic immunosuppressive therapies for the treatment of psoriatic disease in HIV-positive patients, a review of 25 individual cases suggest that these treatments are not only required but also are sufficient to treat some of the most resistant cases. It is possible that with adequate concomitant HAART and monitoring for signs and symptoms of infection, the likelihood of serious infection may be low. Furthermore, biologic agents may have a positive effect over other systemic immunosuppressive agents, such as methotrexate and cyclosporine, in improving CD4 and viral counts when used in combination with HAART. Although randomized controlled trials are necessary, current biologic therapies such as etanercept, adalimumab, infliximab, and ustekinumab may be safe viable options as third-line treatment of severe psoriasis in the HIV-positive population.

The prevalence of psoriasis among human immunodeficiency virus (HIV)–positive patients in the United States is reported to be approximately 1% to 3%, which is similar to the rates reported for the general population.¹ Recalcitrant cases of psoriasis in patients with no history of the condition can be the initial manifestation of HIV infection. In patients with preexisting psoriasis, a flare of their disease can be seen following infection, and progression of HIV correlates with worsening psoriasis.² Psoriatic arthropathy also affects 23% to 50% of HIV-positive patients with psoriasis worldwide, which may be higher than the general population,¹ with more severe joint disease.

The management of psoriatic disease in the HIV-positive population is challenging. The current first-line recommendations for treatment include topical therapies, phototherapy, and highly active antiretroviral therapy (HAART), followed by oral retinoids as second-line agents.³ However, the clinical course of psoriasis in HIV-positive patients often is progressive and refractory²; therefore, these therapies often are inadequate to control both skin and joint manifestations. Most other currently available systemic therapies for psoriatic disease are immunosuppressive, which poses a distinct clinical challenge because HIV-positive patients are already immunocompromised.

There currently are many systemic immunosuppressive agents used for the treatment of psoriatic disease, including oral agents (eg, methotrexate, hydroxyurea, cyclosporine), as well as newer biologic medications, including tumor necrosis factor (TNF) α inhibitors etanercept, adalimumab, infliximab, golimumab, and certolizumab pegol. Golimumab and certolizumab pegol currently are indicated for psoriatic arthritis only. Other newer biologic therapies include ustekinumab, which inhibits IL-12 and IL-23, and secukinumab, which inhibits IL-17A. The purpose of this systematic review is to evaluate the most current literature to explore the efficacy and safety data as they pertain to systemic immunosuppressive therapies for the treatment of psoriatic disease in HIV-positive individuals.

Methods

To investigate the efficacy and safety of systemic immunosuppressive therapies for psoriatic disease in HIV-positive individuals, a PubMed search of articles indexed for MEDLINE (1985-2015) was conducted using the terms psoriasis and HIV and psoriatic arthritis and HIV combined with each of the following systemic immunosuppressive agents: methotrexate, hydroxyurea, cyclosporine, etanercept, adalimumab, infliximab, golimumab, certolizumab pegol, ustekinumab, and secukinumab. Pediatric cases and articles that were not available in the English language were excluded.

For each case, patient demographic information (ie, age, sex), prior failed psoriasis treatments, and history of HAART were documented. The dosing regimen of the systemic agent was noted when different from the US Food and Drug administration–approved dosage for psoriasis or psoriatic arthritis. The duration of immunosuppressive therapy as well as pretreatment and posttreatment CD4 and viral counts (when available) were collected. The response to treatment and adverse effects were summarized.

Results

Our review of the literature yielded a total of 25 reported cases of systemic immunosuppressive therapies used to treat psoriatic disease in HIV-positive patients, including methotrexate, cyclosporine, etanercept, adalimumab, in-fliximab, and ustekinumab (Table). There were no reports of the use of hydroxyurea, golimumab, certolizumab pegol, or secukinumab to treat psoriatic disease in this patient population.

Methotrexate
Eight individual cases of methotrexate used to treat psoriasis and/or psoriatic arthritis in HIV-positive patients were reported.^4-6 Duvic et al⁶ described 4 patients with psoriatic disease that was treated with methotrexate with varying efficacy. One patient developed toxic encephalopathy, which improved after discontinuation of methotrexate; however, he died 5 months later from pneumocystis pneumonia. In this early study, none of the 4 patients were on antiretroviral therapy for HIV.⁶

In the cases reported by Masson et al⁴ and Maurer et al,⁵ 4 patients were treated with a single antiretroviral agent and received appropriate prophylaxis against opportunistic infections. In 1 case, methotrexate was given at a chemotherapeutic dose of 525 mg once weekly for Kaposi sarcoma.⁴ In 2 of 4 cases, the patients developed pneumocystis pneumonia.^4,5

Cyclosporine
There were 2 case reports of successful treatment of psoriatic disease with cyclosporine in HIV-positive patients.^7,8 Skin and joint manifestations improved rapidly without reports of infection for 2⁷ and 8 years.⁸ Both patients were treated with one antiretroviral agent.^7,8

Etanercept
There were 5 case reports of successful treatment of psoriatic disease with etanercept. In all 5 cases the patients were on HAART, and the CD4 count increased or remained stable and viral count became undetectable or remained stable following treatment.^9-13 In 2 cases, the patient also had hepatitis C virus, which remained stable throughout the treatment period.^9,12 The maximum duration of treatment was 6 years, with only 1 reported adverse event.¹³ In this case reported by Aboulafia et al,¹³ the patient experienced recurrent polymicrobial infections, including enterococcal cellulitis, cystitis, and bacteremia, as well as pseudomonas pneumonia and septic arthritis. Therapy was discontinued at 6 months. Four months after discontinuation of etanercept, the patient died from infectious causes.¹³

Adalimumab
There was 1 case of successful treatment of psoriatic disease with adalimumab in an HIV-positive patient. In this case, the patient was on HAART, and CD4 and viral counts improved substantially after 30 months of treatment.¹⁴

Infliximab
Six individual cases of successful treatment of psoriatic disease with infliximab were reported.^15-17 In a report by Cepeda et al,¹⁵ HIV-positive patients with various rheumatologic diseases were chosen to receive etanercept followed by adalimumab and/or infliximab if clinical improvement was not observed on etanercept. In 3 patients with psoriasis and psoriatic arthritis, inadequate response was observed on etanercept. Two of these 3 patients received adalimumab with only partial response. All 3 were treated with infliximab in the end and showed excellent response. One of the patients experienced facial abscess responsive to antibiotics and was continued on infliximab therapy without further complications. In all 6 cases of infliximab therapy, the patients were on HAART, and CD4 and viral counts improved or remained stable.¹⁵

Ustekinumab
There were 3 case reports of successful treatment of psoriatic disease with ustekinumab in HIV-positive patients on HAART. CD4 and viral counts improved or remained stable.^18-20

Comment

Currently, all of the systemic immunosuppressive therapies approved for psoriatic disease have a warning by the US Food and Drug Administration for increased risk of serious infection. Given such labels, these therapies are not routinely prescribed for HIV-positive patients who are already immunocompromised; however, many HIV-positive patients have severe psoriatic disease that cannot be adequately treated with first- and second-line therapies including topical agents, phototherapy, or oral retinoids.

Our comprehensive review yielded a total of 25 reported cases of systemic immunosuppressive therapies used to treat psoriatic disease in HIV-positive patients including methotrexate, cyclosporine, etanercept, adalimumab, in-fliximab, and ustekinumab. Although data are limited to case reports and case series, some trends were observed.

Efficacy
In most of the cases reviewed, the patients had inadequate improvement of psoriatic disease with first- and second-line therapies, which included antiretrovirals alone, topical agents, phototherapy, and oral retinoids. Some cases reported poor response to methotrexate and cyclosporine.^4-8 Biologic agents were effective in many such cases.

Safety
Overall, there were 11 cases in which the patient was not on adequate HAART while being treated with systemic immunosuppressive therapy for psoriatic disease.^4-8,15 Of them, 3 were associated with serious infection while on methotrexate.^5,6 There was only 1 report of serious infection¹³ of 14 cases in which the patient was on concomitant HAART. In this case, which reported polymicrobial infections and subsequent death of the patient, the infections continued after discontinuing etanercept; thus, the association is unclear. Interestingly, despite multiple infections, the CD4 and viral counts were stable throughout treatment with etanercept.¹³

From reviewing the 4 total cases^5,6,13 of serious infection, HAART appears to be a valuable concomitant treatment during systemic immunosuppressive therapy for HIV-positive patients; however, it does not necessarily prevent serious infections from occurring, and thus the clinician’s diligence in monitoring for signs and symptoms of infection remains important.

CD4 and Viral Counts
Although reports of CD4 and viral counts were not available in earlier studies,^4-8 there were 15 cases that reported consistent pretreatment and posttreatment CD4 and viral counts during treatment with etanercept, adalimumab, infliximab, and ustekinumab.^9-20 In all cases, the CD4 count was stable or increased. Similarly, the viral count was stable or decreased. All patients, except 1 by Cepeda et al,¹⁵ were on concomitant HAART.^9-14,16-20

Although data are limited, treatment of psoriatic disease with biologic agents when used in combination with HAART may have beneficial effects on CD4 and viral counts. Tumor necrosis factor has a role in HIV expression through the action of nuclear factor κβ.²¹ An increase in TNF levels is shown to be associated with increased viral count, decreased CD4 count, and increased symptoms of HIV progression, such as fever, fatigue, cachexia, and dementia.²² Although more studies are necessary, TNF-α inhibitors may have a positive effect on HIV while simultaneously treating psoriatic disease. Other cytokines (eg, IL-12, IL-23, IL-17) involved in the mechanism of action of other biologic agents (ustekinumab and secukinumab) have not been shown to be directly associated with HIV activity; however, studies have shown that IL-10 has a role in inhibiting HIV-1 replication and inhibits secretion of proinflammatory cytokines such as IL-12 and TNF-α.²¹ It may be speculated that the inhibition of IL-12 and TNF-α may create a positive feedback effect to increase IL-10, which in turn inhibits HIV replication.

Conclusion

Although there are limited data on the efficacy and safety of systemic immunosuppressive therapies for the treatment of psoriatic disease in HIV-positive patients, a review of 25 individual cases suggest that these treatments are not only required but also are sufficient to treat some of the most resistant cases. It is possible that with adequate concomitant HAART and monitoring for signs and symptoms of infection, the likelihood of serious infection may be low. Furthermore, biologic agents may have a positive effect over other systemic immunosuppressive agents, such as methotrexate and cyclosporine, in improving CD4 and viral counts when used in combination with HAART. Although randomized controlled trials are necessary, current biologic therapies such as etanercept, adalimumab, infliximab, and ustekinumab may be safe viable options as third-line treatment of severe psoriasis in the HIV-positive population.

Over the last decade we have come to understand the nature of psoriasis as a systemic inflammatory condition rather than as simply a skin disease. With this concept, we have continued to identify systemic comorbidities associated with psoriasis, including cardiovascular risk, diabetes mellitus, and metabolic syndrome. As dermatologists, we must serve as the gatekeeper for our patients with psoriasis and help to screen for comorbidities as well as provide appropriate counseling and referral.

Of the potential benefits of novel systemic therapies for psoriasis, the potential for addressing comorbid conditions with these treatments is critically important. Therefore, when I discuss psoriasis treatments, I always review and emphasize the anti-inflammatory effects of these agents. Although we know that psoriasis increases the risk for vascular inflammation and major adverse cardiovascular events (MACEs), it has been unclear if psoriasis duration affects these risks.

Egeberg et al¹ utilized 2 resources to understand the effect of psoriasis duration on vascular disease and cardiovascular events: a human imaging study and a population-based study of cardiovascular disease events. In the first part of the study, patients with psoriasis (N=190) underwent fludeoxyglucose F 18 positron emission tomography/computed tomography. Next, MACE risk was examined using nationwide registries (adjusted hazard ratio in patients with psoriasis [n=87,161] vs the general population [n=4,234,793]). In the imaging study, participants had low cardiovascular risk by traditional risk scores. The authors found that vascular inflammation as demonstrated by the imaging system was significantly associated with disease duration (β=.171; P=.002). In the population-based study, psoriasis duration had a strong relationship with MACE risk (1.0% per additional year of psoriasis duration [hazard ratio, 1.010; 95% confidence interval, 1.007-1.013]). The researchers reported that every standard deviation increase in disease duration increased the target-to-background ratio by 2.5%, which translated into an absolute increase of approximately 10% in future adverse events.¹

Therefore, the authors concluded that there were negative effects of psoriasis duration on vascular inflammation and MACEs,¹ which suggests that the cumulative duration of low-grade chronic inflammation may accelerate vascular disease development and MACEs. The authors therefore noted that providers should consider inquiring about duration of disease to counsel for heightened cardiovascular disease risk in psoriasis patients.¹

We have some evidence that therapeutic intervention may be useful. Wu et al² compared MACE risk in psoriasis patients receiving methotrexate or tumor necrosis factor α (TNF-α) inhibitors. They also assessed the impact of TNF-α inhibitor treatment duration on MACE risk. The authors concluded that psoriasis patients receiving TNF-α inhibitors had a lower MACE risk compared to those receiving methotrexate. Cumulative exposure to TNF-α inhibitors was associated with a reduced risk for MACEs.²

The findings of these studies are poignant and help to further emphasize the importance of proper identification and treatment of psoriasis and its comorbidities. This information also adds an element of urgency to the way we look at this disease and demonstrates that we must intervene as soon as possible in this process.

Over the last decade we have come to understand the nature of psoriasis as a systemic inflammatory condition rather than as simply a skin disease. With this concept, we have continued to identify systemic comorbidities associated with psoriasis, including cardiovascular risk, diabetes mellitus, and metabolic syndrome. As dermatologists, we must serve as the gatekeeper for our patients with psoriasis and help to screen for comorbidities as well as provide appropriate counseling and referral.

Of the potential benefits of novel systemic therapies for psoriasis, the potential for addressing comorbid conditions with these treatments is critically important. Therefore, when I discuss psoriasis treatments, I always review and emphasize the anti-inflammatory effects of these agents. Although we know that psoriasis increases the risk for vascular inflammation and major adverse cardiovascular events (MACEs), it has been unclear if psoriasis duration affects these risks.

Egeberg et al¹ utilized 2 resources to understand the effect of psoriasis duration on vascular disease and cardiovascular events: a human imaging study and a population-based study of cardiovascular disease events. In the first part of the study, patients with psoriasis (N=190) underwent fludeoxyglucose F 18 positron emission tomography/computed tomography. Next, MACE risk was examined using nationwide registries (adjusted hazard ratio in patients with psoriasis [n=87,161] vs the general population [n=4,234,793]). In the imaging study, participants had low cardiovascular risk by traditional risk scores. The authors found that vascular inflammation as demonstrated by the imaging system was significantly associated with disease duration (β=.171; P=.002). In the population-based study, psoriasis duration had a strong relationship with MACE risk (1.0% per additional year of psoriasis duration [hazard ratio, 1.010; 95% confidence interval, 1.007-1.013]). The researchers reported that every standard deviation increase in disease duration increased the target-to-background ratio by 2.5%, which translated into an absolute increase of approximately 10% in future adverse events.¹

Therefore, the authors concluded that there were negative effects of psoriasis duration on vascular inflammation and MACEs,¹ which suggests that the cumulative duration of low-grade chronic inflammation may accelerate vascular disease development and MACEs. The authors therefore noted that providers should consider inquiring about duration of disease to counsel for heightened cardiovascular disease risk in psoriasis patients.¹

We have some evidence that therapeutic intervention may be useful. Wu et al² compared MACE risk in psoriasis patients receiving methotrexate or tumor necrosis factor α (TNF-α) inhibitors. They also assessed the impact of TNF-α inhibitor treatment duration on MACE risk. The authors concluded that psoriasis patients receiving TNF-α inhibitors had a lower MACE risk compared to those receiving methotrexate. Cumulative exposure to TNF-α inhibitors was associated with a reduced risk for MACEs.²

The findings of these studies are poignant and help to further emphasize the importance of proper identification and treatment of psoriasis and its comorbidities. This information also adds an element of urgency to the way we look at this disease and demonstrates that we must intervene as soon as possible in this process.

Over the last decade we have come to understand the nature of psoriasis as a systemic inflammatory condition rather than as simply a skin disease. With this concept, we have continued to identify systemic comorbidities associated with psoriasis, including cardiovascular risk, diabetes mellitus, and metabolic syndrome. As dermatologists, we must serve as the gatekeeper for our patients with psoriasis and help to screen for comorbidities as well as provide appropriate counseling and referral.

Of the potential benefits of novel systemic therapies for psoriasis, the potential for addressing comorbid conditions with these treatments is critically important. Therefore, when I discuss psoriasis treatments, I always review and emphasize the anti-inflammatory effects of these agents. Although we know that psoriasis increases the risk for vascular inflammation and major adverse cardiovascular events (MACEs), it has been unclear if psoriasis duration affects these risks.

Egeberg et al¹ utilized 2 resources to understand the effect of psoriasis duration on vascular disease and cardiovascular events: a human imaging study and a population-based study of cardiovascular disease events. In the first part of the study, patients with psoriasis (N=190) underwent fludeoxyglucose F 18 positron emission tomography/computed tomography. Next, MACE risk was examined using nationwide registries (adjusted hazard ratio in patients with psoriasis [n=87,161] vs the general population [n=4,234,793]). In the imaging study, participants had low cardiovascular risk by traditional risk scores. The authors found that vascular inflammation as demonstrated by the imaging system was significantly associated with disease duration (β=.171; P=.002). In the population-based study, psoriasis duration had a strong relationship with MACE risk (1.0% per additional year of psoriasis duration [hazard ratio, 1.010; 95% confidence interval, 1.007-1.013]). The researchers reported that every standard deviation increase in disease duration increased the target-to-background ratio by 2.5%, which translated into an absolute increase of approximately 10% in future adverse events.¹

Therefore, the authors concluded that there were negative effects of psoriasis duration on vascular inflammation and MACEs,¹ which suggests that the cumulative duration of low-grade chronic inflammation may accelerate vascular disease development and MACEs. The authors therefore noted that providers should consider inquiring about duration of disease to counsel for heightened cardiovascular disease risk in psoriasis patients.¹

We have some evidence that therapeutic intervention may be useful. Wu et al² compared MACE risk in psoriasis patients receiving methotrexate or tumor necrosis factor α (TNF-α) inhibitors. They also assessed the impact of TNF-α inhibitor treatment duration on MACE risk. The authors concluded that psoriasis patients receiving TNF-α inhibitors had a lower MACE risk compared to those receiving methotrexate. Cumulative exposure to TNF-α inhibitors was associated with a reduced risk for MACEs.²

The findings of these studies are poignant and help to further emphasize the importance of proper identification and treatment of psoriasis and its comorbidities. This information also adds an element of urgency to the way we look at this disease and demonstrates that we must intervene as soon as possible in this process.

Biologic agents have provided patients with moderate to severe psoriasis with treatment alternatives that have improved systemic safety profiles and disease control¹; however, case reports of associated neurologic complications have been emerging. Tumor necrosis factor α (TNF-α) inhibitors have been associated with central and peripheral demyelinating disorders. Notably, efalizumab was withdrawn from the market for its association with fatal cases of progressive multifocal leukoencephalopathy (PML).^2,3 It is imperative for dermatologists to be familiar with the clinical presentation, evaluation, and diagnostic criteria of neurologic complications of biologic agents used in the treatment of psoriasis.

Leukoencephalopathy

Progressive multifocal leukoencephalopathy is a fatal demyelinating neurodegenerative disease caused by reactivation of the ubiquitous John Cunningham virus. Primary asymptomatic infection is thought to occur during childhood, then the virus remains latent. Reactivation usually occurs during severe immunosuppression and is classically described in human immunodeficiency virus infection, lymphoproliferative disorders, and other forms of cancer.⁴ A summary of PML and its association with biologics is found in Table 1.^5-13 Few case reports of TNF-α inhibitor–associated PML exist, mostly in the presence of confounding factors such as immunosuppression or underlying autoimmune disease.^10-13 Presenting symptoms of PML often are subacute, rapidly progressive, and can be focal or multifocal and include motor, cognitive, and visual deficits. Of note, there are 2 reported cases of ustekinumab associated with reversible posterior leukoencephalopathy syndrome, which is a hypertensive encephalopathy characterized by headache, altered mental status, vision abnormalities, and seizures.^14,15 Fortunately, this disease is reversible with blood pressure control and removal of the immunosuppressive agent.¹⁶

Demyelinating Disorders

Clinical presentation of demyelinating events associated with biologic agents are varied but include optic neuritis, multiple sclerosis, transverse myelitis, and Guillain-Barré syndrome, among others.^17-28 These demyelinating disorders with their salient features and associated biologics are summarized in Table 2.^17-20,22-28 Patients on biologic agents, especially TNF-α inhibitors, with new-onset visual, motor, or sensory changes warrant closer inspection. Currently, there are no data on any neurologic side effects occurring with the new biologic secukinumab.²⁹

Conclusion

Biologic agents are effective in treating moderate to severe plaque psoriasis, but awareness of associated neurological adverse effects, though rare, is important to consider. Physicians need to be able to counsel patients concerning these risks and promote informed decision-making prior to initiating biologics. Patients with a personal or strong family history of demyelinating disease should be considered for alternative treatment options before initiating anti–TNF-α therapy. Since the withdrawal of efalizumab, no new cases of PML have been reported in patients who were previously on a long-term course. Dermatologists should be vigilant in detecting signs of neurological complications so that an expedited evaluation and neurology referral may prevent progression of disease.

Biologic agents have provided patients with moderate to severe psoriasis with treatment alternatives that have improved systemic safety profiles and disease control¹; however, case reports of associated neurologic complications have been emerging. Tumor necrosis factor α (TNF-α) inhibitors have been associated with central and peripheral demyelinating disorders. Notably, efalizumab was withdrawn from the market for its association with fatal cases of progressive multifocal leukoencephalopathy (PML).^2,3 It is imperative for dermatologists to be familiar with the clinical presentation, evaluation, and diagnostic criteria of neurologic complications of biologic agents used in the treatment of psoriasis.

Leukoencephalopathy

Progressive multifocal leukoencephalopathy is a fatal demyelinating neurodegenerative disease caused by reactivation of the ubiquitous John Cunningham virus. Primary asymptomatic infection is thought to occur during childhood, then the virus remains latent. Reactivation usually occurs during severe immunosuppression and is classically described in human immunodeficiency virus infection, lymphoproliferative disorders, and other forms of cancer.⁴ A summary of PML and its association with biologics is found in Table 1.^5-13 Few case reports of TNF-α inhibitor–associated PML exist, mostly in the presence of confounding factors such as immunosuppression or underlying autoimmune disease.^10-13 Presenting symptoms of PML often are subacute, rapidly progressive, and can be focal or multifocal and include motor, cognitive, and visual deficits. Of note, there are 2 reported cases of ustekinumab associated with reversible posterior leukoencephalopathy syndrome, which is a hypertensive encephalopathy characterized by headache, altered mental status, vision abnormalities, and seizures.^14,15 Fortunately, this disease is reversible with blood pressure control and removal of the immunosuppressive agent.¹⁶

Demyelinating Disorders

Clinical presentation of demyelinating events associated with biologic agents are varied but include optic neuritis, multiple sclerosis, transverse myelitis, and Guillain-Barré syndrome, among others.^17-28 These demyelinating disorders with their salient features and associated biologics are summarized in Table 2.^17-20,22-28 Patients on biologic agents, especially TNF-α inhibitors, with new-onset visual, motor, or sensory changes warrant closer inspection. Currently, there are no data on any neurologic side effects occurring with the new biologic secukinumab.²⁹

Conclusion

Biologic agents are effective in treating moderate to severe plaque psoriasis, but awareness of associated neurological adverse effects, though rare, is important to consider. Physicians need to be able to counsel patients concerning these risks and promote informed decision-making prior to initiating biologics. Patients with a personal or strong family history of demyelinating disease should be considered for alternative treatment options before initiating anti–TNF-α therapy. Since the withdrawal of efalizumab, no new cases of PML have been reported in patients who were previously on a long-term course. Dermatologists should be vigilant in detecting signs of neurological complications so that an expedited evaluation and neurology referral may prevent progression of disease.

Biologic agents have provided patients with moderate to severe psoriasis with treatment alternatives that have improved systemic safety profiles and disease control¹; however, case reports of associated neurologic complications have been emerging. Tumor necrosis factor α (TNF-α) inhibitors have been associated with central and peripheral demyelinating disorders. Notably, efalizumab was withdrawn from the market for its association with fatal cases of progressive multifocal leukoencephalopathy (PML).^2,3 It is imperative for dermatologists to be familiar with the clinical presentation, evaluation, and diagnostic criteria of neurologic complications of biologic agents used in the treatment of psoriasis.

Leukoencephalopathy

Progressive multifocal leukoencephalopathy is a fatal demyelinating neurodegenerative disease caused by reactivation of the ubiquitous John Cunningham virus. Primary asymptomatic infection is thought to occur during childhood, then the virus remains latent. Reactivation usually occurs during severe immunosuppression and is classically described in human immunodeficiency virus infection, lymphoproliferative disorders, and other forms of cancer.⁴ A summary of PML and its association with biologics is found in Table 1.^5-13 Few case reports of TNF-α inhibitor–associated PML exist, mostly in the presence of confounding factors such as immunosuppression or underlying autoimmune disease.^10-13 Presenting symptoms of PML often are subacute, rapidly progressive, and can be focal or multifocal and include motor, cognitive, and visual deficits. Of note, there are 2 reported cases of ustekinumab associated with reversible posterior leukoencephalopathy syndrome, which is a hypertensive encephalopathy characterized by headache, altered mental status, vision abnormalities, and seizures.^14,15 Fortunately, this disease is reversible with blood pressure control and removal of the immunosuppressive agent.¹⁶

Demyelinating Disorders

Clinical presentation of demyelinating events associated with biologic agents are varied but include optic neuritis, multiple sclerosis, transverse myelitis, and Guillain-Barré syndrome, among others.^17-28 These demyelinating disorders with their salient features and associated biologics are summarized in Table 2.^17-20,22-28 Patients on biologic agents, especially TNF-α inhibitors, with new-onset visual, motor, or sensory changes warrant closer inspection. Currently, there are no data on any neurologic side effects occurring with the new biologic secukinumab.²⁹

Conclusion

Biologic agents are effective in treating moderate to severe plaque psoriasis, but awareness of associated neurological adverse effects, though rare, is important to consider. Physicians need to be able to counsel patients concerning these risks and promote informed decision-making prior to initiating biologics. Patients with a personal or strong family history of demyelinating disease should be considered for alternative treatment options before initiating anti–TNF-α therapy. Since the withdrawal of efalizumab, no new cases of PML have been reported in patients who were previously on a long-term course. Dermatologists should be vigilant in detecting signs of neurological complications so that an expedited evaluation and neurology referral may prevent progression of disease.