What's the difference between AHA and BHA exfoliants?

AHAs (like glycolic and lactic acid) are water-soluble and work mainly on the skin's surface to smooth texture and even tone, making them popular for dullness and fine lines. BHA (salicylic acid) is oil-soluble, so it penetrates into pores, which is why it's frequently chosen for blackheads, congestion, and oily or acne-prone skin. Many shoppers use one of each on alternating days rather than layering both at full strength.