Beta Hydroxy Acid (BHA) is a compound that belongs to the group of hydroxy acids and is used in skincare products to exfoliate the skin and clear away dead cells, impurities, and residue. BHA is oil-soluble, which allows it to penetrate deeper into the skin than other exfoliants, such as alpha hydroxy acids. BHA can also help to reduce inflammation and reduce the appearance of discoloration, wrinkles, and other signs of aging.

Beta Hydroxy Acid (Wikipedia)

Not to be confused with butylated hydroxyanisole.

A beta hydroxy acid or β-hydroxy acid (BHA) is an organic compound that contains a carboxylic acid functional group and hydroxy functional group separated by two carbon atoms. They are closely related to alpha hydroxy acids, in which the two functional groups are separated by one carbon atom.

3-Hydroxypropionic acid, a simple beta hydroxy acid

In cosmetics, the term beta hydroxy acid refers specifically to salicylic acid, which is used in some "anti-aging" creams and acne treatments. It is used to combat inflammation.

Upon dehydration, beta-hydroxy acids yield an alpha-beta unsaturated acid.