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Your Guide to Alpha Hydroxy Acids (AHAs) and How TheyWork

We love the thrill of the new. We also love what really, truly works. Here'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.

BY B R O O K E L E P O E R T R E N C H A N D K A R A N E SV I G

October 23, 2017

Photos: Getty Images/Courtesy of brands

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Your Skin Doesn't Have to Peel With a Peel

While 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 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—but 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.

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Dmitry Ageev

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The Percentage of Acid Isn't Everything

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An 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—no 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-

Bernstein, 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.)

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Even the Supersensitive Can Use Them

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"Acids don't work like retinoids, which repair skin by kick-starting inflammation," says 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, which slows

their penetration into skin. (We like Ole Henriksen Invigorating Night Transformation Creme.) 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.

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One Acid is Better Than the Rest

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Magnanimous 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 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 Malin &

Goetz Glycolic Acid Pads to help clear pores and retexturize skin. Some dermatologists believe that no one talks

about how glycolic acid 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, thickens the

epidermis and dermis, and evens skin tone. (Shhhh.)

Hero Images

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Acids Do Nothing for Deep Wrinkles

Now for the reality check: Over-the-counter acid products — even most doctor's-office peels — cannot 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."

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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."

GARO

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They Work Wonders Below the Neck

To treat a blotchy chest, extend your AHA face cream a few inches south. Clear up bacne (or, worse, buttne)

with a salicylic acid body wash, like the classic Neutrogena Body Clear 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—they'll just get inflamed. Instead, apply a lotion with AHAs or BHAs — we love

AmLactin Alpha Hydroxy Therapy Moisturizing Body Lotion — to unclog the pores and dissolve the dry skin.

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K E Y W O R D S S K I N C A R E AC I D S L AC T I C AC I D S A L I CY L I C AC I D C I T R I C AC I D G LYC O L I C AC I D