Star power: These acids, often derived from fruit or milk sugars, dissolve the "glue" between the complexion-dulling dead skin cells that accumulate with age, allowing them to be sloughed off, revealing fresh skin. Discoloration is minimized, skin feels smoother, and pores can look smaller. Overall, skin is more luminous.
What to look for on the label: Glycolic, malic, citric and lactic acids. Glycolic is the most commonly used because it yields good results with little irritation.
For best results: Add an AHA lotion or cream to your daily skincare regimen, or do an at-home AHA peel once a week (or more, if your skin isn't too sensitive). Many dermatologists recommend using an AHA lotion in the morning so your nighttime treatment (whether a retinoid, basic moisturizer, or both) can penetrate more effectively. Both retinoids and AHAs exfoliate the skin, so ease into a regimen that includes the two to avoid redness and peeling. AHAs are great to use on your neck (where the skin is generally too thin to tolerate a retinoid), and can smooth irritation like keratosis pilaris (those little bumps you might have on the backs of your arms) as well as ashy elbows and knees.
You should know: Cleansers containing AHAs aren't in contact with the skin long enough to have any effect. To get results, invest in a cream instead.
Peter Thomas Roth Max Complexion Correction Pads ($36; peterthomasroth.com)
Beauty Rx Skincare by Dr. Schultz Daily Exfoliating Body Therapy Lotion ($50; beautyrx.com)