According to their chemical structure, hydroxyacids correspond to organic carboxylic acids characterized as the α-and β-types (AHA and BHA) according to the position of the hydroxyl group (OH) with regard to the acid (COOH) moiety. Globally, both categories exhibit almost similar biologic effects. These compounds are available worldwide, and likely have been for centuries, as dermatologic and cosmetic ingredients. Their acceptance by dermatologists, other physicians, cosmetologists, and consumers contrasts with the limited independent, well-controlled studies demonstrating their mechanisms of action and their long-term benecial effects.