Understanding Alpha-Hydroxy Acids
The skin-rejuvenating properties of certain alpha-hydroxy acids have been known for centuries. Cleopatra allegedly bathed in spoiled milk, which contains lactic acid, and the women of the French court washed their faces in spoiled wine, which contains tartaric acid. Today, alpha-hydroxy acids (AHAs) are widely used in skin care products. They are the most popular ingredient to enter that marketplace in recent years. In 1996, researchers Perricone and DiNardo reported that approximately forty-five companies were manufacturing over two hundred AHA-containing products, ranging from over-the-counter moisturizers and cosmetics to chemical peels administered by physicians.
Alpha-hydroxy acids are weak organic acids. Although they are found throughout nature in sugar cane (glycolic acid), in sour milk (lactic acid), and in fruits (malic, citric and tartaric acids), the AHAs used in dermatologic and cosmetic products are usually synthetically produced.
The principal cosmetic actions of alpha-hydroxy acids on the skin are increased exfoliation and moisturization, which have the following effects:
- Increased exfoliation Low-concentration alpha-hydroxy acids appear to facilitate shedding (exfoliation) of the outer layer of the surface of the skin (stratum corneum) by interfering with inter-cellular bonding, thereby reducing corneocyte cohesion at the lower level of the stratum corneum. Corneocytes are the cells, arranged in multiple layers, that make up the stratum corneum. Higher concentrations of alpha-hydroxy acids further reduce corneocyte cohesion and cause the thickened, hyperkeratotic stratum corneum to shed in sheet-like fragments, becoming thinner and more compact. In general, lower concentration AHA products simply accelerate cell loss and increase exfoliation, resulting in cosmetically improved skin.
- Moisturization Alpha-hydroxy acids are useful as moisturizers on the face and body. The moisturizing qualities of cosmetic AHA formulations help diminish the appearance of fine lines and maintain the skin’s proper moisture level. Moisturization helps relieve rough and flaky skin conditions; softens dry, cracked and sun-damaged skin; and maintains the proper moisture level in healthy skin.
Today, the use of alpha-hydroxy acids has expanded to consumer lotions and creams that are used to moisturize dry skin, diminish the appearance of fine lines and wrinkles, improve skin tone and texture, and restore a youthful glow to the skin.
Alpha-hydroxy acids remain an effective treatment for ichthyosis. Formulations containing up to 12% glycolic acid, lactic acid, and its derivatives are typically used. A reduction in epidermal thickness is seen on histological examination within two weeks of the start of twice-daily topical applications of AHAs. A soaking bath once or twice a week helps to remove scales from areas where they are tightly adherent. With sustained treatment, normal or near-normal thickness and appearance of the epidermis can be achieved and maintained. Dr. Van Scott and Dr. Yu’s research found that this regimen could be as effective, and often more effective than, systemic therapy with a retinoid.
Reprinted with permission from: Kneedler, J., Sky, S., Sexton, L (1998). Understanding Alpha-hydroxy Acids. Dermatology Nursing, Volume 10, Number 4, pp. 247-262. Reprinted with permission of the publisher, Jannetti Publications, Inc., East Holly Avenue, Box 56, Pittman, NJ 08071-0056; Phone (856)256-2300; Fax (856) 589-7463. Website: www.dnanurse.org.(For a sample copy of the journal, please contact the publisher.)
