Glycolic (gly-CAWL-ihk) acid is a type of alpha hydroxy acid that's derived from sugar cane. It's one of most common substances used for light peels, procedures designed to rejuvenate the skin by removing its outermost layers. Glycolic peels can even out skin tone, fade brown spots, soften the appearance of fine wrinkles, clear pores, and improve mild acne. In this procedure, the acid is applied for several minutes, then neutralized and rinsed or sponged off. There's no recovery time after a glycolic peel, but the results are only temporary. For a more dramatic effect, stronger chemical peels using trichloroacetic (try-klohr-oh-ah-SEE-tihk) acid, or TCA (T-C-A), and phenol (FEE-nawl) can be performed by a dermatologist. These peels go deeper into the skin, are able to treat more severe problems, and require some recovery time. TCA peels are considered a medium peel and may cause swelling and redness that lasts for days. Two or more TCA peels may be needed to achieve the desired result. A phenol peel is generally the deepest peel and also carries the greatest risk. Swelling may be severe and in some people, the complexion may look permanently bleached. Today, phenol peels are often replaced by laser resurfacing, which tends to be safer but produces comparable results.