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"6 Things You Didn&amp;#39;t Know About Acids\\nWe love the thrill of the new. We also love what really, truly works. Here&amp;#39;s why (and how) alpha hydroxy acids (glycolic, lactic, and citric among them) and beta hydroxy acids (namely salicylic) should be your skin-care staples.\\nWhile earlier versions of acid-based exfoliating treatments could make skin visibly slough away, the latest formulas leave skin glowing, not flaking. Many include several [alpha](http://www.allure.com/skin-care/skin-care-glossary) and beta hydroxy acids, rather than just one at a higher concentration. \\\"When you combine acids at lower strengths, they're potentially less irritating,\\\" says New York City dermatologist Dennis Gross. And you don't have to see peeling to see results. \\\"As the acid dissolves the cement between skin cells, you may have thousands of them coming off at the same time\u2014but the shedding is still invisible to the naked eye,\\\" says Neal Schultz, a clinical professor of dermatology at Mount Sinai Medical Center in New York City.\\nAn acid product is only as potent as the free-acid compounds floating around inside it. Too many acid bits and your skin stings and gets red; too few and nothing happens (we mean *nada*\u2014no exfoliation, no glow). So chemists play with the pH, which adjusts the amount of free acids. The ideal pH is between 3 and 4, but it's almost never listed on packaging. So how do you pick a winner? Some experts say your skin should tingle for a few seconds when you apply the product. \\\"If the acid is penetrating, you're going to feel something,\\\" says Eric \\u00adBernstein, a clinical professor of dermatology at the University of Pennsylvania School of Medicine. And expect some instant gratification. \\\"An effective product should leave your skin looking immediately refreshed,\\\" says Gross. ([Discover our six favorites.](http://www.allure.com/beauty-products/skin/2014/best-at-home-acid-skin-care-treatments))\\n\\\"Acids don't work like [retinoids,](http://www.allure.com/skin-care/skin-care-glossary) which repair skin by kick-starting inflammation,\\\" says [Ranella Hirsch,](http://www.allure.com/beauty-products/beauty-product-finder/experts/dermatologist-ranella-hirsch) an assistant clinical professor of dermatology at Boston University School of Medicine. \\\"They dissolve the upper layer of cells to trigger repair.\\\" Plus, unlike with scrubs, the skin is not damaged by abrasives. So if you're sensitive, acids are actually a wise choice. Look for formulas that combine them with an [amino acid,](http://www.allure.com/skin-care/skin-care-glossary) like [arginine,](http://www.allure.com/skin-care/skin-care-glossary) which slows their penetration into skin. (We like __Philosophy Hope in a Jar Night.__) And don't rush in. \\\"Irritation can take a while to show up,\\\" says Hirsch. \\\"You may get to day four, then all of a sudden your skin reacts.\\\" Take a month to ramp up to daily use.\\nMagnanimous girlfriends and pug owners insist that size doesn't matter, but cosmetic chemists disagree. The smaller a molecule, the more easily it gets into the skin. Because [glycolic](http://www.allure.com/skin-care/skin-care-glossary) is the smallest of all the acids, it yields the most dramatic results. \\\"There's a reason glycolic is the acid used the most in anti-aging products and doctor's-office peels,\\\" says Hirsch. \\\"It does the job.\\\" Almost as well as a prescription retinoid, says Schultz. (Try [Avon Anew Clinical Advanced Retexturizing Peel.](http://www.allure.com/beauty-products/skin/2010/avon-anew-clinical-retexturizing-peel)) Some dermatologists believe that no one talks about how [glycolic acid](http://www.allure.com/skin-care/skin-care-glossary) changes the structure of the skin because then the FDA will call it a drug, regulate it, and suddenly we'll need to see a doctor to get it. But the truth is that it regenerates [collagen,](http://www.allure.com/skin-care/skin-care-glossary) thickens the epidermis and dermis, and evens skin tone. (*Shhhh.*)\\nNow for the reality check: Over-the-counter acid products\u2014even most doctor's-office peels\u2014cannot smooth deep lines. \\\"Only fillers and laser procedures can do that,\\\" says Wilma Bergfeld, a senior dermatologist at the Cleveland Clinic. \\\"These compounds can minimize fine lines and fade blotches, but they have limitations.\\\" According to Hirsch, your skin gets the most from acids in your 20s and 30s: \\\"After that, I have patients treat serious damage with a prescription retinoid and refresh their skin with regular peels at home or in my office.\\\"\\nTo treat a blotchy chest, extend your AHA face cream a few inches south. Clear up bacne (or, worse, buttne) with a [salicylic acid](http://www.allure.com/skin-care/skin-care-glossary) body wash: Apply it to dry skin, wait 15 minutes, then get in the shower and rinse. When the backs of your arms feel like a plucked goose, don't try to scrub the bumps away\u2014they'll just get inflamed. Instead, apply a lotion with AHAs or BHAs to unclog the pores and dissolve the dry skin."^^<http://www.w3.org/2001/XMLSchema#string>
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