If you’re particularly into skin care, then you likely already know (and love, and regularly use) exfoliating alpha hydroxy acids and beta hydroxy acids in your routine. However, you may have noticed a rise in a third buzzy, three-letter acronym: PHAs (short for polyhydroxy acids). You may be asking yourself what are they, and how do they differ from their alpha- and beta- brethren? We asked a couple of board-certified dermatologists all about the ingredient, and to make a long story short (although you should definitely familiarize yourself with the below #knowledge), PHAs might be a saving grace if you’ve found that your skin is sensitive to other exfoliating acids.What exactly are PHAs?

“Polyhydroxy acids — aka PHAs — are chemical exfoliants, and are considered ‘cousins’ of alpha hydroxy acids, as they are, in fact, second-generation AHAs,” Shereene Idriss, a dermatologist in New York City, tells Allure. “The most common PHAs are gluconolactone, galactose, and lactobionic acid.”