AHA BHA PHA refers to the three hydroxy acids that are found in various substances in nature, namely Alpha Hydroxy acids, Beta Hydroxy acids, and Poly Hydroxy acids.
Alpha Hydroxy Acids are generally used for exfoliation, as they help break down the bonds between skin cells to allow them to be cleaned easily. Since AHA can smoothen the skin and reduce fine lines and wrinkles, they are perfect for people with aging skin.
Glycolic acid, derived from sugars, and lactic acid, derived from milk and Mandelic acid is derived from bitter almonds.
Like the AHA, Beta Hydroxy Acids too are exfoliators; however, they have a slightly different method of action and offer some different benefits. BHA is able to penetrate the skin more deeply to bestow its beneficial effects on it.
The most commonly used BHA is salicylic acid, which is derived from willow tree bark, wintergreen oil, and sweet birch. Salicylic acid is present in aspirin.
Citric acid, derived from citric fruits such as lemons, oranges, etc can be an AHA or a BHA.
The PHA or Poly Hydroxy Acids is the latest addition to the family of hydroxy acids that are used in skincare. PHA is not much different from the AHA, in terms of both the molecular structure and mechanism of action. Like the latter, it too breaks down the bond between cells to help with exfoliation. And it also shares the hydrating properties of AHA.
The only difference is that PHA has a larger molecular size than AHA, this means it does not penetrate the skin as fast as AHA. This leads to less irritation of the skin, if there is any.
Some of the commonly used PHA include lactobionic acid (derived from the lactose in milk), galactose (a simple sugar), and gluconic acid (naturally found in cells).