Ask any beauty editor what their ride-or-die product is for clear, dewy skin, and they'll give it to you straight: liquid exfoliants. I'm talking alpha or beta hydroxy acids (think: glycolic, lactic, or salicylic) that help treat everything from acne to fine lines and dark spots. But even though they're known as the gentler alternative to physical exfoliants (aka those gritty-ass face scrubs you used in high school), they can still be pretty harsh on highly-sensitive skin. And that's why the somewhat under-the-radar acid that's trending right now is the gentle giant known as polyhydroxy acid (PHA).
PHAs are dubbed "the chill distant cousin" to AHAs, and they're loved for their ability to gently break down dead skin cells with v minimal irritation, meaning they're perfect for folks with ultra-sensitive skin. Sounds pretty cool, right? That's why I immediately hit up Nikhil Dhingra, MD, dermatologist at Spring Street Dermatology in NYC, for the full low-down on PHAs—namely, what they are, how to use 'em, and the best formulas to try immediately. Keep reading for all the deets.
What are polyhydroxy acids?
Polyhydroxy acids are chemical exfoliants, just like AHAs (e.g., lactic and glycolic acids), and BHAs (e.g., salicylic acid). Buuut, they tend to be the gentlest of the three by far. Why? Because they're made up of larger molecules, says Dr. Dhingra, meaning they won't penetrate your skin as deeply.
So, what exactly does PHA—or really any of the acids—do for your skin? Well, regular chemical exfoliation can help brighten up your face and even out your texture, while also helping your other skincare products penetrate your skin more efficiently. Acids are basically liquid gold...if you can tolerate them. Which is why PHAs are so awesome: "Their biggest selling point is that they have a lower risk of irritation, but they still effectively exfoliate the most superficial layers of the skin," says Dr. Dhingra.
The three most common types of PHAs are gluconolactone, galactose, and lactobionic acid, all of which you can find in products like serums, moisturizers, and toners (the options below are a few of my personal faves).
Are PHAs good for the skin?
Here's the thing: Anyone can benefit from the gentle exfoliation of PHAs, but they're especially great for folks who find traditional acids (AHAs and BHAs) too irritating. They're also more hydrating than the majority of chemical exfoliants, so they're safe for skin that's already on the drier side.
And though PHAs aren't really the gold standard for treating and preventing acne (you'll want to look towards glycolic acid, salicylic acid, and/or retinoids for that), they are pretty great at getting rid of post-inflammatory hyperpigmentation (aka those dark marks and spots you get after a zit has healed).
"PHAs can help lift superficial pigmentation after a breakout clears, and they're less likely to cause rashes in the process, which can worsen pigmentary issues," says Dr. Dhingra. "They're also safe for all skin types, including darker skin tones that are prone to hyperpigmentation."
How do you use PHAs?
Even though PHAs are gentler than most chemical exfoliants, they'll still need to be eased slowly into your skincare routine to avoid any irritation—especially if you're prone to rosacea, keratosis pilaris, or eczema. "You want to approach any acids with caution," says Dr. Dhingra. "Start slowly—think: once every 2-3 days—before pushing the limits further." And as with any new ingredient or product, it's never a bad idea to chat with your dermatologist before you kick things off. Better safe than sorry, right?
What can you not mix with PHA?
Okay, here's where things get a liiitle complicated. There's no hard or fast rule when it comes to mixing PHAs with other active ingredients, so it's best to chat with a dermatologist about your specific skin concerns before you cocktail anything yourself.
"The oiliest, most acne-prone skin types can likely tolerate a triple threat of AHAs, BHAs, and PHAs with minimal irritation, but even combining PHA with other actives, like retinoids, can increase the risk of irritation," says Dr. Dhingra. "If you're even remotely prone to rosacea, eczema, dryness, or redness, I'd suggest starting slow with a product that only contains one type of acid."
If your skin can handle something a bit more intense—and you've already cleared it with your dermatologist—you're in luck, because there are actually a handful of PHA toners, serums, and liquids that are also spiked with BHAs and AHAs (like the four top-rated picks below). Just remember: You'll want to add these bbs to your routine slowly—start with every three days and gently build up once you know your skin agrees with it.
The final word
If your skin can't hang with regular exfoliants—or you're just looking for a new way to level-up your exfoliating routine—you should absolutely consider adding in a PHA product. Like Dr. Dhingra says, the smaller molecules in polyhydroxy acids means you're way less likely to experience irritation, redness, or dryness—especially if you haven't had success with AHAs or BHAs in the past. And considering there are so many good PHA-spiked products on the market right now, you officially have no reason not to try one.
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