If you look at the back of the bottle of your nearest facial cleanser, there are probably a ton of ingredients that sound familiar — from salicylic acid to glycolic acid, glycerin and more. One of the more unfamiliar ingredients you might happen upon, however, are PHAs, also known as polyhydroxy acids. This buzzy skin-care additive has been under the skin-care junkie microscope for the latter half of 2018 and into 2019, so we reached out to dermatologist Nava Greenfield, M.D., at Schweiger Dermatology to find out what exactly this ingredient works to do — and here’s what we learned. What Are PHAs?PHAs are exfoliant acids, similar to AHAs (like glycolic acid) or BHAs (like salicylic acid) that work to slough away dead skin cells and help prepare the skin for hydrating products. PHAs can be found in myriad skin-care products, from cleansers to exfoliators, moisturizers and more. What Do PHAs Do?Unlike AHAs and BHAs, “PHAs appear to be less irritating on the skin and are therefore used for more sensitive skin types,” says Dr. Greenfield. Due to their larger molecules, they don’t penetrate the skin in the same way as other acids might, which helps them be better tolerated. It’s worth noting, though, that while “their unique chemical structure makes them more gentle, they also can be less effective,” says Dr. Greenfield. Who Can Benefit From PHAs?PHAs benefit a variety of skin types, but Dr. Greenfield urges you to speak to your dermatologist about your own skin concerns before taking the dive. “Although products with PHAs claim to be safe for atopic and rosacea-prone skin, always try a test spot before applying them all over your face,” she says. And depending on your skin tone, you’ll also want to test PHAs carefully, as “darker skin tones need to use more caution with any type of acid product because it can result in hyperpigmentation.”How to Incorporate PHAs Into Your Skin Care RoutineAs far as your routine goes, Dr. Greenfield recommends following the directions on the bottle. “Some daily moisturizers have PHAs as an ingredient, which would be used daily while others are meant to be used as exfoliators weekly,” she says. Where to Find PHAsAs PHAs become more trendy in the skin-care space, they’ve also become more prevalent in products. From Glossier Solution to the Avocado Melt Mask by Glow Recipe, it seems like there’s a new PHA-packed skin care product everyday. “PHAs, BHAs and AHAs all can provide benefit to specific skin conditions when used properly and appropriately,” says Dr. Greenfield, “but I have seen patients try out products they buy on the internet at home and end up with severe burns that take many months and cosmetic treatments to treat,” she says, so it’s key to test them out and speak to your dermatologist before committing to the acid skin care move — as gentle as it might be.Read MoreThe Best 10 Face Moisturizers of 2018How To Get Rid of Acne ScarsThe Best Drugstore Makeup Remover Wipes 
