ABSTRACT

Since our publication on alpha hydroxy acids (AHAs) for topical treatment of ichthyosis in 1974, AHAs have been used as primary ingredients or in combination with other topical agents for various cosmetic and dermatological indications, ranging from dry skin, skin smoothing, acne, age spots, fine lines, and wrinkles to photoaging [1-3]. Because of the acidic

nature, a topical formulation containing an AHA usually has a pH of below 2.0, and the formulation might cause skin stinging and/or irritation on repeated topical application to sensitive or atopic skin. In most commercial products, the AHA is partially neutralized with an alkali to raise the pH to 3.5 to 4.5. One frequently asked, but very important, question is the relationship between the pH and topical efficacy of an AHA formulation. This chapter is intended to answer this question and also to discuss related issues, including a slow-release amphoteric system containing an AHA.