The alpha hydroxy acids (AHAs) are organic carboxylic acids having one hydroxyl group attached to the alpha position of the carboxylic carbon atom. Alpha hydroxy acids are naturally occurring products present in sugar cane juice, sour milk, tomato juice, grapes, and apples. Gly-colic acid, a 2-carbon molecule, and the smallest of the AHA compounds, has gained widespread acceptance as a superficial exfoliant and peeling agent [38,39].
AHAs induce changes in the epidermis and dermis. They cause exfoliation of the stratum corneum. Dermal effects have also been demonstrated. In a study by Ditre et al. , patients applied a lotion containing 25% glycolic, citric, or lactic acid to one forearm and a placebo lotion to the other for 6 months. Thickness of forearm skin was measured throughout the study. Treatment with AHAs caused an approximate 25% increase in skin thickness. The epidermis was thicker and papillary dermal changes included increased thickness, increased acid mucopolysaccharides, improved quality of elastic fibers, and increased density of collagen. No inflammation was evident. Treatment with AHAs produced significant reversal of epidermal and dermal markers of photoaging. Glycolic acid improves the tone and texture of the skin. It is used as a mono-therapy, or in combination with retinoids and other bleaching agents for photodamage.
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