One of the most commonly used organic acids used on the skin, lactic acid, has been used for over 3 decades. Originally derived from milk or plant-derived sugars, this gentle exfoliating acid can be used in peels, serums, masks, and toners, and has the additional benefit of hydrating the skin. Lactic acid is formulated in concentrations from 2% to 50%; however, because of its large molecular size, it doesn’t penetrate the deeper layers of the dermis to the same extent as the other alpha-hydroxy acids (AHAs), such as glycolic acid. Thus, it is one of the gentler exfoliants and one that can be used in sensitive skin or darker skin types.
Despite its mild peeling effects, lactic acid is best used to treat xerotic skin because of its function as a humectant, drawing moisture into the stratum corneum. Similar to the other AHAs, lactic acid has also been shown to decrease melanogenesis and is a gentle treatment for skin hyperpigmentation, particularly in skin of color. Side effects include peeling, stinging, erythema, photosensitivity, and hyperpigmentation when improperly used.
Very little clinical research has been reported in the last 20 years as to the uses and benefits of lactic acid in skincare. In my clinical experience, daily use of lactic acid is more effective and has more long-term benefits for hydration and rejuvenation of the skin than the other AHAs. Concentrations of 10%-15% used daily on the skin as a mild exfoliant and humectant have shown to improve texture, decrease pigmentation and improve fine lines – without thinning of the skin seen with the deeper dermal penetrating acids.
Confusion in the market has also risen as many over-the-counter brands have included ammonium lactate in their portfolio of moisturizers. Ammonium lactate is a combination of ammonium hydroxide and lactic acid, or the salt of lactic acid. A comparativeevaluating the difference between 5% lactic acid and 12% ammonium lactate for the treatment of xerosis showed that ammonium lactate was significantly more effective at reducing xerosis. It is widely used in the treatment of keratosis pilaris, calluses, xerosis, and ichthyosis.
Widespread use of lactic acid has not gotten as much glory as that of glycolic acid. However, in clinical practice, its functions are more widespread. It is a much safer acid to use, and its added benefit of increasing hydration of the skin is crucial in its long-term use for both photoaging and the prevention of wrinkles. With any acid, the exfoliating properties must be treated with adequate hydration and barrier repair.
The intrinsic moisturizing effect of lactic acid makes it a much more well-rounded acid and that can be used for longer periods of time in a broader spectrum of patients.
Dr. Lily Talakoub and Dr. Naissan O. Wesley are cocontributors to this column. Dr. Talakoub is in private practice in McLean, Va. Dr. Wesley practices dermatology in Beverly Hills, Calif. This month’s column is by Dr. Talakoub. Write to them at. They had no relevant disclosures.