PHA stands for polyhydroxy acid, a type of chemical exfoliant designed to deliver the skin-smoothing and anti-aging benefits of traditional acids without the stinging, redness, or irritation that often comes with them. PHAs are sometimes called “next generation” hydroxy acids because they work similarly to the AHAs you may already know (like glycolic acid) but are gentler on the skin’s surface. The most common PHAs in skincare products are gluconolactone, lactobionic acid, and galactose.
How PHAs Work on Skin
Like all hydroxy acids, PHAs exfoliate by loosening the bonds between dead skin cells on the surface, helping them shed more evenly. What makes PHAs different is their molecular size. Gluconolactone, the most widely used PHA, has a molecular weight of 178, compared to 76 for glycolic acid. That’s more than twice as large. Because the molecule is bigger, it penetrates the skin more gradually and stays closer to the surface rather than sinking deep into lower layers. This slower, shallower penetration is the main reason PHAs cause less burning and stinging than glycolic or lactic acid.
Beyond exfoliation, PHAs pull double duty. Their chemical structure allows them to attract and hold water against the skin, functioning as humectants. They also have antioxidant properties through a process called chelation, which helps neutralize metal ions that can contribute to skin damage. So while a traditional AHA is primarily an exfoliant, a PHA exfoliates, hydrates, and offers some protective benefit all at once.
PHAs vs. AHAs vs. BHAs
All three belong to the hydroxy acid family, but they differ in important ways:
- AHAs (glycolic acid, lactic acid) are water-soluble and penetrate quickly. They’re effective for sun-damaged skin, fine lines, and uneven texture. Concentrations in skincare range from 2% to 70% depending on the product. The tradeoff is that AHAs, particularly glycolic acid, can increase your skin’s sensitivity to UV light and frequently cause irritation at higher strengths.
- BHAs (salicylic acid) are fat-soluble, meaning they can cut through oil and penetrate into pores. That makes them especially useful for acne-prone or oily skin. Salicylic acid does not appear to increase sun sensitivity the way glycolic acid does.
- PHAs (gluconolactone, lactobionic acid) deliver anti-aging and smoothing effects comparable to AHAs but with significantly less irritation. They add hydration and antioxidant benefits that AHAs and BHAs don’t provide on their own.
If you’ve tried glycolic acid serums or peels and found them too harsh, PHAs are the logical next option. They won’t produce results as quickly, since they work at the surface rather than penetrating deeply, but for many people the gentler approach is worth the patience.
Who Benefits Most From PHAs
PHAs were specifically developed for people who couldn’t tolerate traditional AHAs. That makes them a strong fit for sensitive, dry, or reactive skin types. People with conditions like rosacea or eczema, who often have to avoid chemical exfoliants entirely, may find PHAs usable where glycolic or salicylic acid would trigger flare-ups. The humectant effect also makes PHAs appealing if your skin tends to feel tight or dehydrated after using other acids.
PHAs can also be paired with other treatments. Clinical use has combined them with procedures like laser resurfacing and microdermabrasion to enhance results and support recovery, since their moisturizing and antioxidant properties help the skin heal without added irritation.
What PHAs Help With
The core benefits overlap heavily with AHAs: smoother texture, reduced fine lines, more even skin tone, and a brighter overall appearance. Because they exfoliate the outermost layer of dead cells, PHAs can also help other products in your routine absorb more effectively. The hydration boost is a distinct advantage. If your skin looks dull and feels rough but also tends toward dryness, a PHA addresses both problems simultaneously rather than forcing you to choose between exfoliation and moisture.
PHAs are less effective for deep acne or congested pores, where salicylic acid’s ability to dissolve oil inside the pore gives it a clear advantage. They’re also not the fastest route to dramatic resurfacing results. If you have significant sun damage or deep wrinkles and your skin can handle stronger acids, a higher-concentration AHA will likely produce more visible change in less time.
Concentrations and How to Use Them
PHA concentrations in commercial products typically range from 0.5% to 10%, though most formulas fall between 2% and 5%. The right percentage depends on what else is in the product and how often you plan to use it. A daily moisturizer with 2% gluconolactone works differently than a weekly treatment serum at 8% or 10%. If you’re new to chemical exfoliants, starting at the lower end and using the product every other day gives your skin time to adjust.
You’ll find PHAs in toners, serums, moisturizers, and cleansers. Leave-on products like serums and creams give the ingredient more time to work than a rinse-off cleanser, so they tend to deliver more noticeable results. Because PHAs are gentler and less likely to cause photosensitivity than glycolic acid, they’re more forgiving if you occasionally skip sunscreen, though daily SPF is still a good idea whenever you’re using any exfoliating acid.
The Two Main PHAs in Products
Gluconolactone is the PHA you’ll encounter most often. It’s the one with the most research behind it for anti-aging and skin smoothing. It exfoliates gently while forming a moisture-attracting layer on the skin’s surface.
Lactobionic acid is the other common PHA, and it tends to appear in products targeting aging skin specifically. It shares the humectant and antioxidant chelation properties of gluconolactone but is often highlighted for its ability to support skin firmness. Both are well-tolerated, and many PHA products contain one or both. When scanning ingredient lists, these are the two names to look for.
What to Realistically Expect
PHAs work more gradually than AHAs because of their slower penetration and surface-level action. You’re unlikely to see dramatic overnight change. Most people notice improved hydration within the first week or two, with texture and tone improvements building over several weeks of consistent use. The experience of using PHAs is notably different from stronger acids: no tingling, no visible peeling, no redness. For some people this feels like the product isn’t doing anything, but the exfoliation is happening, just at a pace the skin can handle without visible inflammation.
If you’ve been using an AHA and want to switch, there’s no required transition period. You can swap directly. Going the other direction, from PHA to AHA, is where you’d want to introduce the stronger acid slowly to avoid irritation your skin isn’t accustomed to.