Exfoliation has been moving in one direction for a few years now: gentler. Harsh scrubs and high-strength acids are giving way to slower, kinder options, and polyhydroxy acids — PHAs — are at the front of that shift. They loosen dead skin cells like other acids do, but they work more slowly and tend to sting less. Here is what PHAs are, how they compare to AHAs and BHAs, and whether they belong in your routine.
What PHAs Are
PHAs are a group of exfoliating acids that includes gluconolactone, lactobionic acid and galactose. Chemically they are close relatives of alpha hydroxy acids like glycolic and lactic acid, which is why they work in a similar way: they loosen the bonds between dead cells on the skin’s surface so they shed more evenly.
The key difference is size. PHA molecules are larger than glycolic acid, so they move into the skin more slowly. That usually means less stinging and redness, and a gentler, more gradual effect.
PHAs exfoliate like AHAs, but more slowly and gently, and they also help skin hold water. They are a good first exfoliant for sensitive or dry skin.
What PHAs Do Well
- Gentle exfoliation for smoother texture and a brighter look over time.
- Hydration: their structure attracts and holds water, so they behave partly like a humectant.
- Antioxidant and chelating activity, especially for lactobionic acid, which may help protect skin from some environmental stress.
- Better tolerance: they are often suitable for people whose skin reacts to glycolic acid.
What they do not do: PHAs are not strong enough to replace a prescription treatment, and they will not clear clogged pores as effectively as salicylic acid, which dissolves in oil and works inside the pore.
PHA vs AHA vs BHA
- PHAs (gluconolactone, lactobionic acid): largest and gentlest. Best for sensitive, dry or reactive skin.
- AHAs (glycolic, lactic, mandelic acid): water-soluble surface exfoliants. Glycolic is the strongest; lactic and mandelic are gentler.
- BHA (salicylic acid): oil-soluble, gets into pores. Best for blackheads and oily or acne-prone skin.
Many people end up using two: a BHA for the T-zone or breakout areas, and a PHA or gentle AHA elsewhere. Our exfoliation guide explains how to combine them without overdoing it.
Who PHAs Suit Best
- Sensitive skin that stings with glycolic acid.
- Dry or dehydrated skin that wants exfoliation without tightness.
- Beginners trying an exfoliant for the first time.
- Anyone using a retinoid who wants gentle extra exfoliation on alternate nights.
If you have rosacea or eczema, PHAs are generally better tolerated than stronger acids, but check with your dermatologist first, and stop if your skin flares.
How to Use a PHA
- Start two or three times a week, in the evening, on clean dry skin.
- Build to daily use only if your skin stays comfortable.
- Follow with a moisturizer; PHAs pair well with ceramides and niacinamide.
- Avoid stacking it with other acids or a retinoid on the same night until you know how your skin reacts.
- Wear broad-spectrum sunscreen every morning, as with any exfoliant.
Not sure whether a product already contains an acid? Paste its ingredient list into the free ingredient checker before you add another exfoliant on top.
Frequently asked questions
What is PHA in skincare?
PHA stands for polyhydroxy acid, a group of gentle exfoliating acids that includes gluconolactone, lactobionic acid and galactose. They loosen dead surface cells like AHAs do, but more slowly, and they also help skin hold water.
Is PHA better than AHA?
Not better, gentler. PHAs suit sensitive and dry skin that reacts to glycolic acid. AHAs like glycolic acid work faster and more strongly, which some people want and others cannot tolerate.
Can you use PHA every day?
Many people can, but start two or three times a week and increase only if your skin stays comfortable. Always follow with moisturizer and use daily sunscreen.
Can I use PHA with retinol?
Yes, but not on the same night at first. Alternate them, for example PHA on one evening and retinol on the next, and see how your skin responds before combining them.