Salicylic Acid, which is the only Beta Hydroxy Acid (BHA), is unlike the water soluble AHA’s in that it is oil soluble and can penetrate sebum-clogged pores, exfoliate the cells within them, and clear whiteheads and blackheads, making it especially beneficial for treating oily skins and acne. Give your skin a seasonal overhaul with Ava MD Radical Departure Kit ($125, avamd.com and select Barneys), a dermatologist-designed professional-caliber system using AHA’s, BHA and Retinol (Vitamin A) to achieve smooth, clear, glowing skin when used for two weeks every few months.