Alpha Hydroxy Acids. The two-edged sword a closer look to an anti aging element

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Alpha hydroxy acids (AHA's) have been described in the literature for the treatment of a number of conditions in which abnormal keratinization consistently contributes to pathogenesis. These include adult acne scars. An study performed by Tung RC et al evaluated the efficacy and skin tolerance of the alpha hydroxy acid gluconolactone 14% in solution for acne treatment when compared with its vehicle (placebo) and 5% benzoyl peroxide lotion. The results of this study showed that both AHA's and benzoyl peroxide had a significant effect in treatment of acne by reducing the number of lesions (inflamed and non-inflamed). Furthermore, fewer side-effects were experienced by acne patients treated with AHA's in comparison with benzoyl peroxide.

Alpha hydroxy acids are botanical substances that induce mild inflammation and accelerate exfoliation with little or no burning or stinging, said Paul Lazar, MD, emeritus clinical professor of dermatology at Northwestern University Medical School, Chicago, Ill. "A little inflammation isn't bad. Alpha hydroxy acids improve skin coloring and even skin tone," said Lazar, who served for many years as director of the American Medical Association's Committee on Cosmetics and Cutaneous Health. "A little edema," he noted, "puffs out fine wrinkles." Also effective as an acne treatment. But concerns remain, he said, about whether chronic low-grade irritation has adverse lasting effects, such as increasing blood vessel dilation, whether the alpha hydroxy acids harm the skin's barrier functions, and how much they increase sun sensitivity.

The most widely used of these chemicals are the alpha-hydroxy acids (AHAs). Beta-hydroxy acid, better known as salicylic acid, long a part of the dermatologist's acne treatment armamentarium, is a newer addition to cosmetic products, as are combination-hydroxy acids and poly-hydroxy acids.

The concentration of hydroxy acids in a product is directly related to its potential to cause peeling and irritation, said Zoe Draelos, MD, clinical associate professor of dermatology . But concentration is not the only factor, she said, as preparations can be changed by buffering or through neutralization. Low concentrations, such as 1% AHAs, have been shown to alter the pH of the outer 3 layers of the stratum corneum, she said, while the higher concentrations available in some cosmetic products, such as 10% AHAs, have been shown to affect the pH of the stratum corneum 10 to 20 layers deep. Application of a glycolic acid preparation to the skin, she said, has been reported to yield a 2.4% concentration in the stratum corneum, an 11.6% concentration in the epidermis, and an 8.6% concentration in the dermis. "This degree of biological activity," she said, "does not fit with the current definition of cosmetics" (Skin Aging. 1998;6:45-47).

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