Your Ultimate Guide to AHAs, BHAs, and PHAs
If applying something caustic-sounding to your face gives you a little pause, know this: skin-care acids are some of the most versatile and hardworking ingredients in the complexion playbook. They have the power to zap zits, blast away brown spots, Magic Eraser away fine lines, plus deliver intense hydration and/or a healthy glow—almost instantaneously. By whisking away dead cells from your skin’s surface, acids also clear the way for active ingredients to do their thing; essentially, they help other products perform better. Here, a primer on alpha hydroxy acids (AHAs), beta hydroxy acids (BHAs), polyhydroxy acids (PHAs), and hyaluronic acid (HA)—plus, our favorites of each to shop now.
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Matteo Scarpellini1/14How often to use AHAs, BHAs, and PHAs
Regardless of which acid—or acids—you decide to try, it’s best to introduce them into your routine gradually, starting once or twice a week. And because acids (excluding hyaluronic acid) remove the top layer of skin, they can make your complexion more UV-sensitive. Always, always slather on SPF of at least 30 during the day to protect your newfound glow. (Here are a few of our favorites.)
Matteo Valle2/14If you want something that does it all, consider AHAs (aka the workhorses)
Most alpha hydroxy acids are naturally derived, coming from such sources as sugar, milk, and fruit, and they’re much more gentle—and better for sensitive skin—than scrubs. “Physical exfoliants sand the skin’s surface,” says New York dermatologist Dennis Gross, M.D., whereas acids break apart the bonds that hold dead skin in place without causing collateral irritation. And they have an added bonus when used regularly: “By increasing cell turnover, you’re going to encourage the creation of new collagen,” says Dr. Gross. “So you’ll see a firming effect over time.”
Glycolic acid has the smallest molecule size of all the AHAs and gives the best bang for your buck. Since it can penetrate so deeply, glycolic acid benefits include tackling sun damage, and dispersing the pigment at the deep basal level of the dermis where sunspots and melasma are created. Milder AHAs with larger molecules, such as lactic acid and malic acid, are home runs for supersensitive types, and they’re often used to round out weaker glycolic formulations. “Using multiple acids together at low concentrations is going to be much less irritating than using a higher percentage of glycolic acid alone,” explains Dr. Gross.
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Matteo Scarpellini6/14If your main concern is acne, try BHA.
There’s only one beta hydroxy acid—salicylic acid—but it’s an antiinflammatory, anti-acne warrior, and it can be used on its own or combined with AHAs. “BHA is lipophilic, so it’s drawn to oils,” says New York City dermatologist Robert Anolik, M.D. “That means it will not only exfoliate the top layer but also target the sebaceous glands down in the pores, clearing the clogs that create whiteheads and blackheads while also helping fade the pink marks that are left over from old outbreaks.”
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Greg Scaffidi9/14For really sensitive skin, stick with PHAs.
“Polyhydroxy acids have larger molecules than AHAs, so they work only on the most superficial layer of skin,” says Dr. Anolik. “They’re so gentle, they can even be used even by people with rosacea or eczema.” In addition to minimizing the risk of red cheeks, PHAs are also hydrating, making them a great bet for anyone with super-dry skin. On ingredient labels, “look for gluconolactone and lactobionic acid,” says dermatologist Joshua Zeichner, M.D.
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Matteo Valle12/14Need extra hydration? Go with hyaluronic acid.
Unlike other acids, hyaluronic acid doesn’t buff away dead skin cells. Instead, HA “is a sugar that has skin-hydrating and plumping properties,” says Dr. Zeichner. Its famed ability to hold 1,000 times its weight in water, drawing H2O into the skin and holding it there like a magnet, is what makes it a popular—practically necessary—ingredient in serums and moisturizers. Oh, and its soothing, smoothing properties make it great to slather on after using an exfoliating acid to clear away all of the gunk.
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