What's the difference between PHAs and AHAs?

PHAs (polyhydroxy acids) are essentially a newer, gentler generation of AHAs. They exfoliate the same way — loosening dead surface cells — but their molecules are much larger, so they absorb slowly and stay near the surface. That means similar smoothing and brightening benefits with far less of the stinging and irritation that stronger AHAs can cause.

Are PHAs good for sensitive skin and rosacea?

They're often the best-tolerated exfoliating option for reactive skin. Because they penetrate slowly and gently, PHAs have been studied specifically for use on sensitive skin, and they also act as humectants that draw in moisture. If glycolic or even lactic acid is too much for you, a PHA is worth trying — patch test first, as always.

Do PHAs work as well as stronger acids?

For deep resurfacing, no — that's the trade-off for their gentleness. PHAs work more slowly and subtly, so they're less suited to stubborn concerns that need a stronger acid or a prescription. What they do well is provide steady, low-irritation exfoliation and hydration for skin that can't handle anything harsher.

PHAs (Polyhydroxy Acids), Explained

PHAs — polyhydroxy acids — are the exfoliating acids you reach for when even the "gentle" ones are too much. Think of them as the next generation of AHAs: same basic job, much softer touch. If your skin is sensitive, easily irritated, or prone to redness, they may be the most useful acids you're not yet using.

What PHAs are

PHAs are a family of water-soluble chemical exfoliants closely related to AHAs, with the two most common being gluconolactone and lactobionic acid. Their key feature is molecular size: PHA molecules are larger than AHA molecules, so they're absorbed slowly and act mostly at the skin's surface. That gives similar exfoliating benefits without the stinging and irritation associated with stronger acids — which is why they've been studied specifically for use on sensitive skin (PMC, 2023; PMC, 2012).

What they do

Exfoliate gently. Like AHAs, PHAs help dissolve the bonds between dead surface cells, so skin looks smoother, brighter, and more even — but the large molecule size keeps redness and flaking to a minimum (PMC, 2023).
Hydrate. PHAs are also humectants — they attract and hold water — so they support moisture rather than leaving skin tight. That pairs well with hyaluronic acid and ceramides.
Play nicely with sensitive skin. A gluconolactone-based formula was shown to be well tolerated and biologically safe for cosmetic use, reinforcing the "gentle enough for reactive skin" reputation (PMC, 2023).

Who benefits most

Sensitive, reactive, or redness-prone skin (including rosacea-prone) that can't tolerate AHAs.
Dry or dehydrated skin wanting exfoliation that doesn't strip.
Beginners and anyone with a compromised barrier who wants the mildest possible acid.

How to use it

Start low and slow. Even the gentlest acid should be introduced gradually — a couple of times a week, building as tolerated.
When: typically at night, on clean dry skin, followed by moisturizer — see what order to apply your skincare.
Still wear sunscreen. Any exfoliation leaves fresh skin at the surface, so daily sunscreen remains part of the deal.
Pairs well with niacinamide, panthenol, and other soothing, barrier-supporting ingredients.

Honest expectations

PHAs trade power for tolerability. They won't resurface skin as dramatically or as fast as glycolic acid, and stubborn concerns will likely need something stronger. But for skin that flushes, stings, or peels at the first sign of an acid, PHAs offer something genuinely valuable: steady, gentle exfoliation and hydration you can actually keep using. Gentle-but-consistent beats strong-but-abandoned.

When to see a dermatologist

PHAs are cosmetic ingredients, not a treatment for a medical condition. If you have persistent redness, a rosacea-like flush, ongoing irritation, or breakouts that aren't improving, see a board-certified dermatologist. And get any new, changing, or non-healing spot looked at in person.

Not sure whether your skin needs gentle exfoliation, more hydration, or barrier repair? A dermatrix.life skin assessment reads photos you upload and gives you a private, plain-language summary to help you focus. It's informational only, not a diagnosis, and never a substitute for a professional. (How it works.)