Clin Dermatol. 2009 Sep-Oct; 27(5): 495-501Green BA, Yu RJ, Van Scott EJThe hydroxyacids are represented by the alpha-hydroxyacids, beta-hydroxyacids, polyhydroxy acids, and bionic acids. Together, these ingredients form a class of compounds with unparalleled benefits to the skin and unprecedented usage in the cosmeceutical market in cosmetic and therapeutic formulations alike. The most commonly used hydroxyacid is glycolic acid, an alpha-hydroxyacid that has been used extensively in cosmetic antiaging formulations, moisturizers, and peels, and in treatment products to improve hyperpigmentation and acne. The newer polyhydroxy and bionic acids offer the benefits of alpha-hydroxyacids without irritation, making them suitable for use on sensitive skin, rosacea, and after cosmetic procedures. They also provide additional antioxidant/chelation, barrier strengthening, and moisturizing effects. Bionic acids inhibit matrix metalloproteinase enzymes in skin, providing a preventative antiaging benefit. The hydroxyacids as a class can be combined with therapeutically active materials and cosmetic procedures to increase therapeutic effects and improve tolerability and outcomes of medicinal agents and procedures.