ABSTRACT
INTRODUCTION Alpha hydroxy acids (AHAs) and retinol (free or palmitate ester) are frequently used ingredients in cosmetic products. These products are often advertised to reduce fine lines and wrinkles and to improve skin condition in general. Chemically, the two classes of ingredients are quite different. AHAs are generally smaller, more hydrophilic molecules, whereas retinol and its esters, such as retinyl palmitate, are much more lipophilic. Skin absorption studies of these chemicals have increased our understanding of the potential local and systemic exposure from topical use of products containing these ingredients. In addition, studies have been conducted to evaluate the effect of hydroxy acids on skin sensitivity to UV light.
