Alpha-hydroxy acid

α-Hydroxy acids, or alpha hydroxy acids (AHAs), are a class of chemical compounds that consist of a carboxylic acid substituted with a hydroxyl group on the adjacent carbon. They may be either naturally occurring or synthetic. AHAs are well known for their use in the cosmetics industry. They are often found in products that aid in the reduction of wrinkles as well as to soften strong, defining lines and improve the overall look and feel of the skin. They are also used as chemical peels available in a dermatologist's office, beauty and health spas and home kits, which usually contain a lower concentration of around 4%. Effective results through continuous treatment have resulted in AHAs being a successful & developmental method of curbing harsh ageing effects in the skin & cosmeceutical industry.

Understanding skin structure and cutaneous aging is helpful to a discussion of the topical action of AHAs. Human skin has two principal components, the avascular epidermis and the underlying vascular dermis. Cutaneous aging, while having epidermal concomitants, seems to involve primarily the dermis and is caused by intrinsic and extrinsic aging factors.

AHAs are a group of organic carboxylic compounds. AHAs most commonly used in cosmetic applications are typically derived from food products including glycolic acid (from sugar cane), lactic acid (from sour milk), malic acid (from apples), citric acid (from citrus fruits) and tartaric acid (from grape wine). For any topical compound to be effective, including AHA, it must penetrate into the skin where it can act on living cells. Bioavailability (influenced primarily by small molecular size) is an important factor in a compound's ability to penetrate the top layer of the skin. Glycolic acid, having the smallest molecular size, is the AHA with greatest bioavailability and penetrates the skin most easily; this largely accounts for the popularity of this product in cosmetic applications.

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