Alpha-hydroxy and beta-hydroxy acids like glycolic, lactic, and salicylic acid are by no
means bad for the skin—they're amazing exfoliators that can brighten, reduce wrinkles, and prevent and treat breakouts. However, according to Darden, they're often over-used. "I am a huge fan of chemical exfoliants overall, but people tend to use them too often. You don’t need to use them morning and night, every single day," she says. "Depending on your skin type and the other products you’re using, you really only need to exfoliate one-to-two times a week."