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What Are Polyhydroxy Acids (PHAs)? The Full 101 On These Exfoliants

If you’re a skincare enthusiast, you’re probably aware of the benefits of regular exfoliation and the properties of beta hydroxy acids (BHAs) and alpha-hydroxy acids (AHAs). But as far as our love goes for those acids, AHAs and BHAs aren’t the most skin-friendly actives and can cause sensitivities, especially in problematic skin. Luckily, a new exfoliation team has joined the game that promises to deliver the same skin-renewing power as its predecessors, AHAs and BHAs, but in a more delicate fashion and without adverse effects — meet polyhydroxy acids (PHAs). Without further ado, here’s what you need to know about PHAs in skincare, their benefits, and how to use them to maximize their potential. 

What are PHAs in skincare?

Briefly, polyhydroxy acids are a class of chemical exfoliators that act gently on the skin. Just like AHAs and BHAs, polyhydroxy acids remove dead cells buildup from the outermost skin layer, resulting in a smoother and more even texture. Lactobionic acid, galactose, and gluconolactone are the most commonly used PHAs in skincare formulations and the most sought-after exfoliants for dry, sensitive skin due to their gentle nature.

The benefits of PHAs for skin

PHAs have unique perks, such as bigger molecular size and more surface-level penetration, that make them suitable for all skin types. But they are especially effective for those who can’t tolerate powerful acids like glycolic acid. Besides, PHAs are humectants too, meaning they attract water and hydrate (similar to lactic acid), so they work like a charm for dehydrated skin. Here are more benefits that polyhydroxy acids come with:

  • Exfoliate: This is the most notable skin benefit of PHAs, as they prevent the buildup of dead cells and protect from age spots, acne, and dullness. They also aid in promoting collagen formation, needed for maintaining skin firm and elastic.
  • Combat glycation: PHAs also combat glycation, a process that can weaken and decrease elastin and collagen levels.
  • Anti-inflammatory: Although PHAs are well known for their exfoliating power, they also possess a slew of anti-inflammatory and antioxidant activities, making them great multitaskers.
  • Maintain skin hydration: PHAs are humectants (aka they maintain moisture reserves); they help create the most radiant complexions by enhancing radiance and plumping skin.
  • Don’t cause irritations: PHAs are gentler than other exfoliants due to their bigger molecular size. They’ll never go quite as far as a straight-up AHA because of this, and they’ll take somewhat longer to sink in.
  • Reduce acne: Acne occurs when pores get blocked with a mix of dead cells, sebum, and bacteria. Hence, the exfoliating benefits of PHAs can help unclog pores and prevent breakouts.
  • Even skin tone: PHAs are also effective for skin discolorations such as dark spots and hyperpigmentation since they remove cells that have been affected by excess pigment. By the same token, PHAs may fade superficial acne scars. 

Side effects

The best part about PHAs in skincare? They’re known to have minimal adverse effects. PHAs don’t penetrate deeply into the skin; instead, they gently wash away any dirt that may have accumulated on the surface. However, because they are still acids, you should perform a patch test first if you have sensitive skin to see how your skin reacts to PHAs. 

How to use PHAs

Few irritations are expected the first time when you use a new acid. However, if PHAs cause significant irritation in increasing and persistent redness, peeling, and itching, it indicates that the product is either too harsh or should be used less frequently. 

Pay close attention to your skin for signals that you should reduce your usage and limit use to once per week if you use other acids in your regimen. However, as with any new ingredient, start gently to avoid irritating your skin. Because PHAs are less harsh than other acids, you can safely use them three to four times per week. Keep in mind that the appropriate strength varies depending on your skin tolerance.

PHAs uses in skincare

PHAs are among the most adaptable acids in skincare, which means you can use them in conjunction with almost any other actives. For instance, when treating acne or photoaging, PHAs can be used with retinoids, while for hyperpigmentation, PHAs can be paired with vitamin C

PHAs work best in leave-on products, giving them enough time to break the connections that hold the cells together. But you can use them in any sort of product, including liquid exfoliants, toners, masks, and moisturizers, among others. Many AHA solutions contain PHAs to clear up the surface-level dirt that AHAs cannot remove. Sometimes, PHAs are added to a non-peeling product to work as an additional exfoliating element, allowing dead cells to be washed away. And in some instances, PHAs serve as the primary selling pitch. Speaking of which, we’ve covered the best PHA products that vow to clear and restore the skin here.

  1. Grimes PE, Green BA, Wildnauer RH, Edison BL. The use of polyhydroxy acids (PHAs) in photoaged skin. Cutis. 2004 Feb;73(2 Suppl):3-13. PMID: 15002656.
  2. Edison BL, Green BA, Wildnauer RH, Sigler ML. A polyhydroxy acid skin care regimen provides antiaging effects comparable to an alpha-hydroxyacid regimen. Cutis. 2004 Feb;73(2 Suppl):14-7. PMID: 15002657.
  3. Antiaging bionic and polyhydroxy acids reduce nonenzymatic protein glycation and skin sallowness, Journal of the American Academy of Dermatology, Volume 70, Issue 5, Supplement 1, 2014, Page AB22, ISSN 0190-9622, https://doi.org/10.1016/j.jaad.2014.01.092.
Who wrote this?
Picture of Jordan Baker
Jordan Baker
Jordan Baker is a nationally certified pharmacy technician who has worked in retail pharmacy for the past two years. Throughout her past, while studying microcopy and even field research in the Amazon, her passion for beauty has only grown. She may have been the only person wearing makeup in the rainforest, but it cemented her commitment to the beauty community. Her own troubled teenage years with cystic acne have put her on a mission to educate others towards a more holistic skincare journey. She now enjoys writing content with a scientific eye.
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