Salicylic acid (BHAs)
When it comes to beta hydroxy acids (BHAs), for all intents and purposes, we are referring to salicylic acid. Salicylic acid is by far the most common and available BHA. While salicylic acid will not eliminate acne on its own, it can help treat acne primarily through its ability to exfoliate the skin, and when used alongside other acne treatments, may help them work better by increasing their penetration into the skin. It can be found in over-the-counter products in 0.5 to 2% strength. An esthetician/cosmetician, nurse, or doctor can also apply it in a professionally-administered chemical peel in 20% to 70% strength.
Note: If you go to the drugstore, you'll notice most acne treatment products contain salicylic acid. This is because the FDA has only approved four acne treatment active ingredients for sale over-the-counter (benzoyl peroxide, sulfur, and resorcinol are the other three), and out of the four approved treatments, it causes the fewest side effects. However, just because a products says "acne treatment" on its label doesn't mean it will completely clear the skin. If you decide to use a salicylic acid acne treatment product, keep your expectations realistic, and seriously consider using it alongside other proven treatment regimens that can completely clear the skin.