MOST ACIDS FALL INTO ONE OF TWO CATEGORIES: AHAS AND BHAS. “Alpha hydroxy acids, a.k.a. AHAs, are a group of natural and synthetic ingredients derived from fruits, sugarcane, or milk and work on most skin types, excluding the very sensitive kind,” Dr. Sobel says. AHAs are also water soluble, meaning they’re active just on the skin’s surface (and don’t go any deeper). Common forms of AHAs include glycolic, lactic, citric, and malic.
BETA HYDROXY ACIDS, OR BHAS, are oil soluble and composed of smaller molecules, so they can get way down inside pores to gently shed dead skin, bacteria, sebum, and pore-clogging debris. That’s why they’re especially good for treating overactive, oily skin. “They help de-gunk pores and penetrate deeper to fight breakouts,” Dr. Gross says. “Salicylic acid is a…