In fact, alpha-hydroxy acids (AHAs) are a collective name for many chemical substances, because most of them can be found in natural fruits, hence the name “fruit acids”.
These include glycolic acid extracted from sugarcane, lactic acid extracted from yogurt, tartaric acid obtained from wine, malic acid obtained from apples, and citric acid obtained from citrus fruits, all of which are common ingredients. You can check the ingredients of your skincare products to see if they contain fruit acids. The chemical structure of fruit acids all contain hydroxyl acids (HA).
Known fruit acids can be divided into three categories: alpha-hydroxy acids, beta-hydroxy acids, and poly-hydroxy acids. This classification is based on the position of the hydroxyl (OH) in the molecular structure of the fruit acid. If the hydroxyl is attached to the first carbon, it is called alpha-hydroxy acid; if it is attached to the second carbon, it is called beta-hydroxy acid; if there are multiple hydroxyl groups, it is called poly-hydroxy acid, which is a multiple hydroxyl fruit acid. Later, the abbreviation in English, because the use of alpha and beta is inconvenient, respectively, replaced alpha with the letter A to become AHA, most commonly used are glycolic acid and lactic acid; beta is replaced with the letter B to become BHA, which is salicylic acid; and poly-hydroxy acid’s poly is replaced with the letter P, which is PHA. Common examples include gluconolactone and lactobionic acid. So the abbreviation is AHA, BHA, or PHA for the three categories.
In terms of topical use on the skin, different types of fruit acids have different effects. AHA has moisturizing, antioxidant, keratin metabolism, whitening, and anti-aging functions. Clinical experiments have shown that it can promote keratin metabolism and significantly increase the content of hyaluronic acid and proteoglycans in the dermis, making the skin thicker, and has significant efficacy for solar keratosis. In addition, composite fruit acids such as Jessner’s peel and Miami peel mix AHA and BHA with other effective ingredients, which have significant efficacy for melasma and acne.
There are at least a dozen types of fruit acid peels. As for which fruit acid to use, how long, and how concentrated, it depends on each person’s situation. Some beauty companies promote their single fruit acid as being able to treat acne, increase collagen, and remove freckles, etc. Consumers should understand whether the ingredients have these effects. The following will discuss the functions of different fruit acids.