Alpha hydroxy acids

They may be derived from sugar, as in glycolic (gly-CAWL-ihk) acid; milk, which provides lactic acid; or fruits like apples, which contain malic (MAL*-ihk) acid.

AHAs can reduce fine lines, fade age spots, even out skin tone, and clear blocked pores by sloughing off dead skin cells and increasing the rate at which new cells are brought to the surface. Most over-the-counter AHA products have an acid content of 10 percent or less; those below eight percent are believed to be ineffective. The solutions used by cosmetologists for light peels are limited to a strength of 20 or 30 percent. Peels using 50 to 70 percent AHAs are available only in a dermatologist's office. At the proper strength, AHAs can rejuvenate the skin's appearance, at least temporarily. However, they also appear to increase sun sensitivity, leading to speculation about a greater risk of photoaging or even skin cancer.

Studies are underway to evaluate the long-term effects of AHAs. In the meantime, it's probably best to use such products cautiously. Follow the directions carefully and avoid the sun when possible. Wear a broad-spectrum sunscreen every day. If you experience redness, stinging, itching, or irritation, discontinue the product.