FDA on the Effectiveness and Safety of Alpha Hydroxy Acids (AHAs) in Cosmetics

Why are AHAs used in some cosmetics? Alpha hydroxy acids (AHAs) are commonly used as ingredients in cosmetics and drugs applied to the skin. Products containing AHAs serve a variety of purposes, such as smoothing fine lines and surface wrinkles, improving skin texture and tone, unclogging and cleansing pores, and improving overall skin condition. Sometimes AHAs also help adjust the skin's pH. The most common AHAs in cosmetics are glycolic acid and lactic acid; others include citric acid, hydroxycaprylic acid and hydroxycapric acid. How do AHAs work? Products containing AHAs cause the surface layer of skin to shed. The degree of exfoliation depends on the type and concentration of the AHA, its pH, and the other ingredients in the product. Some AHA-containing products already on the market are used mainly to treat acne, remove scars and fade discoloration. These include some products sold as “peels,” which may contain relatively high concentrations of AHAs or other acids designed to remove the outer layer of skin. Under Section 201(g) of the Federal Food, Drug, and Cosmetic Act, products intended to diagnose, cure, mitigate, treat or prevent disease, or to affect the structure or any function of the body, fall under the legal definition of a drug — for example, products intended to treat acne or to act as a skin lightener. Has the FDA studied the safety of AHAs? Yes. FDA studies covered the following: (1) compared the effect of AHAs applied topically in a cream on the sensitivity of human skin to ultraviolet (UV) radiation against the same cream without AHAs; (2) measured how quickly the skin returned to normal after AHA-containing cream was discontinued; (3) investigated whether AHAs increased UV-induced DNA damage in the skin. These studies confirmed earlier industry research showing that applying AHAs to the skin increases sensitivity to UV light. After four weeks of AHA use, volunteers' sensitivity to UV-induced skin reddening increased by 18%. Likewise, volunteers' sensitivity to UV-induced cell damage on average doubled, with considerable variation between individuals. However, the studies also showed that this increased sensitivity is reversible and does not last long after the AHA cream is discontinued. One week after treatment stopped, researchers found no significant difference in UV sensitivity across different skin sites. The studies did not definitively determine how AHAs cause increased UV sensitivity, though the effect does not appear to involve a sharp increase in UV-induced DNA damage in the skin. Earlier FDA research suggested that cosmetic-type cream bases cause AHAs to penetrate more deeply into the skin than cosmetic solutions that typically do not contain AHAs. However, further research is needed to understand the effect of these cosmetic-type ingredients on AHA-related UV sensitivity. The FDA has also worked with the National Toxicology Program (NTP) to evaluate the safety of long-term AHA use, and continues to review available data on AHAs to address the possibility of increased skin sensitivity to sunlight. How can AHAs be used safely? When using any cosmetic, always follow the instructions carefully and heed any warning statements on the label. If you are using an AHA, applying sunscreen is recommended. As far back as 2005, the FDA issued “Guidance for Industry: Labeling for Cosmetics Containing Alpha Hydroxy Acids.” The purpose of this guidance was to make consumers aware that topical use of AHA-containing cosmetics may increase the skin's sensitivity to sunlight, and to educate manufacturers to help ensure that the labeling of these products is not false or misleading. The FDA recommends that if a cosmetic contains an AHA ingredient and is applied topically to the skin or mucous membranes (such as the lips), its label should bear a statement conveying the following: Sunburn Alert: This product contains an alpha hydroxy acid (AHA) that may increase your skin's sensitivity to the sun and particularly the possibility of sunburn. Use a sunscreen, wear protective clothing and limit sun exposure while using this product and for a week afterwards. The Cosmetic Ingredient Review (CIR) expert panel concluded, based on industry-sponsored research, that consumers can safely use products containing the AHAs glycolic acid and lactic acid if the following conditions are met: 1. The AHA concentration is 10% or less. 2. The final product has a pH of 3.5 or higher. 3. The final product is formulated to protect the skin from increased sun sensitivity, or its packaging instructions tell consumers to use daily sun protection. How can you tell if a cosmetic contains AHAs? Under the authority of the Fair Packaging and Labeling Act (FPLA), the FDA requires an ingredient declaration on cosmetics sold to consumers at the retail level. However, because the FPLA does not apply to products for professional use, the ingredient-declaration requirement does not apply to those products.