AHAs (Alpha Hydroxy Acids) are fruit acids that produce a mild exfoliating effect on the skin. In ordinary over-the-counter beauty products, they are extremely diluted (usually between 2% and 10%) in order to gently slough off superficial dead skin cells and reveal brighter, newer, more refined skin underneath. This has the added effect of increasing cell turnover for a slightly rejuvenating effect. The acids used are usually glycolic acid (from sugar cane); lactic acid (from sour milk and tomato juice); citric acid (from citrus fruits such as lemon and orange); malic acid (from apples) or tartaric acid (from grapes). Used moderately in, say, one product per day, they help refresh the skin surface, improve hydration, reduce fine lines and discolouration, and even improve dermal thickness for a plumper, younger appearance. However, when used in too many products at once (for example, in cleanser, toner, day cream and night cream), their concentrated effects can cause irritation and redness. Qualified beauty therapists and salons also use these fruit acids in stronger concentrations (typically 20%-30%) in anti-ageing peeling treatments, but they are used in the highest concentrations (of 50%-70%) by dermatologists and plastic surgeons. The medical version of the chemical peel produces a controlled burn that peels away the outer skin layers, revealing newer, smoother, tighter skin underneath and thereby reducing lines, wrinkles, crepiness, roughness, discolouration and acne scarring. However, healing may take up to two to three weeks.

Source: Dweck, Anthony. Handbook of Natural Ingredients (Dweck Books 4) . Dweck Data. Kindle Edition.

‍