For oily, breakout-prone skin, BHA is a great choice. But for dry, sun-damaged or lined skin, AHA, or alpha-hydroxy acid, is an ideal exfoliant.
AHA is a water-soluble exfoliant, and it comes in several different forms, including lactic acid, malic acid, citric aced and glycolic acid. Glycolic acid, extracted from sugarcane, and lactic acid, extracted from milk, are the most popular AHAs [source: Paula's Choice]. These ingredients are sometimes used in "chemical peels" performed in spas and dermatologist offices (but chemical peels are a step up from basic exfoliation; they're harsher and should not be performed at home).
You'll find AHAs in lotions, cleansers and toners. They penetrate the skin to chemically free dead skin cells and allow the skin to renew itself, and they do it without risking the loss of too much skin to over-zealous physical exfoliation.
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