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New Age Attitude Toward AHAs

By: Christine Heathman
Posted: July 22, 2008, from the March 2007 issue of Skin Inc. magazine.

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Facial wrinkles have been modified drastically with topical AHAs when applied in a professional peeling procedure and are re-emerging as one of the most promising noninvasive anti-aging approaches for a quick and efficacious result. AHA peeling continues to evolve, and more physicians are offering AHA skin care management in conjunction with Botox and facial fillers because of the immediate results.

The AHA acid test

AHAs perform best at a low pH; therefore, pH is of great importance for achieving a therapeutic outcome. The suggested pH range is between 3 and 5; however, lower levels are very effective but have to be monitored carefully since the lower the pH, the more rapid the erythema produced in the skin.

The acidity depends partly on the concentration of the hydroxy acid and is determined by electrostatic, inductive and steric effects and hydrogen bonding. Besides hydroxy acid concentration, free acid content is another important factor. At pH 3 there is a greater absorption through the skin than at pH 7, as at pH 3 the concentration of free acid is higher. The higher the AHA concentration, the deeper the effect of the solution. Several enzymes such as phosphatases, lipases and transforming growth factor B have maximum activity at pH 5 or lower, and it is possible that an acid environment may activate these mechanisms.

Naturally occurring topical retinoids such as vitamin A (all-trans retinol) and its metabolites (tretinoin) are well-known agents for treatment of mature, changing and photodamaged skin. Retinoids’ long-term application shows benefits similar to those assessed with AHAs.

Glycolic acid

Glycolic acid is the most well-known of the AHAs. Mainly derived from bio-identical chemical constituents, the natural source is best extracted from the sugar cane plant. Glycolic acid has the smallest molecular size, containing only two carbons. This characteristic allows glycolic acid the greatest ability of all the AHAs to penetrate more rapidly, be absorbed deeper and be utilized by the skin.