ABSTRACT

Alpha hydroxy acids (AHAs) occur naturally in a number of fruits (from where they get their ‘eco-friendly’ name of fruit acids) and dairy products. This class of acids contains a number of molecules that have in common the presence of a carboxylic acid group (COOH) and a hydroxy group (OH) in the alpha position relative to the acid group (Figure 6.1). As early as 1946, the application of a 3% lactic acid solution at pH 3.8 was already considered a treatment for ichthyosis, although cosmetic dermatologists only really started using AHAs when in 1974 Van Scott and Yu described how effective they were in the treatment of dry or ichthyotic skin. From then on, the scope of AHAs broadened, and some authors reported their beneficial effects on acne, photoaging and benign hyperplastic epidermal lesions. It was often suggested that AHAs should be used to treat age-related wrinkles and sagging skin. Although the direct target of AHAs seems to be corneodesmosomes, the indirect action of topically applied AHAs affects not only the whole of the epidermis but also the papillary dermis and the pilosebaceous units. However, while all peels produce similar1 histological effects on the different layers of the skin, clinical results clearly show that AHAs, used as light peels, do not improve the skin’s appearance to the same extent as TCA or phenol. Moreover, indications for glycolic acid peels tend to be restricted to the treatment of sun-damaged or acneic skin, especially in patients who

cannot or do not want their skin to flake, often because of their professional activities, which are incompatible with visible peeling.