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Ready to feel more confident when reading your beauty products' ingredient labels? Enter, the Allure Ingredient Index. In this comprehensive guide, you'll find everything you need to know about the most in-demand (and under-the-radar) ingredients in your favorite skin-care products.
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, M.D., a board-certified dermatologist in New York City, tells Allure. "The most common PHAs are gluconolactone, galactose, and lactobionic acid."
Similar to AHAs, PHAs work by exfoliating dead skin cells on the surface, resulting in a more even skin tone and texture, and also help skin-care ingredients penetrate deeper into the layers of your skin, thus boosting their efficacy.
PHAs also fight glycation, a process that takes place when digested sugar permanently attaches to the collagen in your skin and can weaken it, along with elastin levels, according to board-certified dermatologist Patricia Wexler, M.D., in New York City. "They're also rich in antioxidants and stimulate epidermal growth and repair," she adds.
"Their difference lies within their molecular structure," says Dr. Wexler. "The molecules of PHAs are much larger and therefore cannot penetrate as deeply as AHAs and BHAs; they work exclusively on the surface, without disturbing the deeper delicate layers." All of this is to say: They offer less irritation than their acidic counterparts.
An additional benefit of this behavior, according to Dr. Idriss, is that skin does not become more photo-sensitive, or susceptible to damaging UV rays.
Are PHAs suitable for my skin?
The better you understand your skin type and concerns, the easier it'll be to determine what ingredients are best suited for you. "AHAs, such as glycolic acid and lactic acid, penetrate the skin more deeply, while BHAs — salicylic acid being the most popular — are better suited to oilier, acne-prone skin," Dr. Wexler explains. "AHAs are generally preferred for normal to dry skin, and are used due to their affinity to enhance natural moisturizing factors and exfoliate dead cells. BHAs, which are great for oilier skin types, work their way into blocked pores, dissolving sebum and dead skin cells, and help exfoliate acne that can lead to post-inflammatory pigmentation."
As for mixing acids together? Yes, it can be done — you may have noticed products like Glossier's Solution, which contains a cocktail of exfoliating AHAs, BHAs, and PHAs in one does-it-all bottle. However, if that's a little strong for your skin, try taking things slow with either a PHA-based product, like Neostrata's Bionic Face Cream (a favorite of Dr. Idriss's), or one laced with AHAs.
"It is not unusual to see combinations of PHAs and AHAs in the same preparation," Dr. Wexler says, which is clear in the Zelens PHA+ Resurfacing Facial Pads. She recommends it for patients looking to address fine lines, dullness, and enlarged pores.
Sensitive skin types may benefit best from PHAs
The unique properties of PHAs mentioned above — larger molecule size, surface level penetration — make them ideal for virtually all skin types, especially if you've experienced sensitivity in the past with an AHA- or BHA-based product. "PHAs are wonderful alternatives to both AHAs and BHAs if you tend to have very sensitive skin and could not tolerate many chemical exfoliants," Dr. Idriss says. "Additionally, PHAs are an attractive option for those with dry skin as they are humectants, meaning they attract water and are ultimately moisturizing."
And because it's a gentler ingredient, Dr. Wexler even encourages patients with "dry, itchy skin," eczema, or atopic rosacea to try PHAs to help smooth and retexturize skin without irritation with a product like Exuviance's Moisture Balance Toner. Here's to having it all when it comes to skin care.
More on chemical exfoliators:
- Your Guide to Alpha Hydroxy Acids (AHAs) and How They Work
- The Best At-Home Face Peels Under $20
- Here's Why Chemical Peels Are the Secret to Perfect Skin
Now, see how face masks has evolved within the last 100 years:
