Polyhydroxy Acids (PHAs) in Skincare

What are polyhydroxy acids?

Polyhydroxy acids are a family of hydroxy acids used in skincare for surface exfoliation and moisture support. The shorthand names PHA and PHAs describe the category rather than one single ingredient.

Gluconolactone is the PHA shoppers are most likely to see on an ingredient list and has the clearest direct human evidence for everyday skincare. Lactobionic acid is also commonly grouped with PHAs in cosmetic marketing, although scientific literature sometimes describes it separately as a bionic acid.^[1]

That distinction matters because gluconolactone, lactobionic acid, galactose, and other related materials are not interchangeable versions of one active. Evidence for one should not automatically be applied to another.

What do polyhydroxy acids do for skin?

PHAs are used mainly to loosen surface buildup so rough or dull-looking skin feels smoother and looks brighter.

Gluconolactone also has humectant properties. Small human studies found increased skin hydration after topical gluconolactone treatments, with no clear hydration advantage for 30% over 10% in the tested peel-style regimen.^[2]

That combination of exfoliation and moisture support makes PHAs a possible option if you find stronger acid formulas drying or uncomfortable.

PHAs are not established as universal acne treatments, scar removers, pigment treatments, wrinkle treatments, or replacements for sunscreen. A finished product may address one of those concerns because of the complete formula or product-specific evidence.

What the evidence says about polyhydroxy acid skincare

The evidence is most useful for gluconolactone, and much of it comes from small studies or specific treatment regimens.

A split-face study in 16 healthy women compared 10% and 30% gluconolactone solutions over three treatments. Both concentrations increased hydration, and the higher concentration did not produce significantly greater hydration.^[2]

A later split-face study in 16 women using the same concentrations found reductions in transepidermal water loss at several facial sites after three peel treatments. Again, the higher concentration did not consistently outperform the lower one.^[3]

A 12-week clinical study compared a gluconolactone-containing PHA regimen with a glycolic-acid AHA regimen in people with photoaged skin. Both regimens improved several appearance measures. The glycolic-acid regimen performed better on some endpoints, while the PHA regimen caused less stinging and burning.^[4]

That supports gluconolactone as a potentially better-tolerated exfoliating option for some shoppers. It does not prove that every PHA product is gentler than every AHA product because complete multi-product regimens were compared, and the authors were affiliated with NeoStrata.

There is also older acne evidence. A 1992 double-blind trial in 150 people compared 14% gluconolactone lotion, its vehicle, and 5% benzoyl peroxide for mild-to-moderate acne. Both active treatments reduced inflammatory and non-inflammatory lesions, with fewer adverse effects reported with gluconolactone.^[5]

That trial is more than three decades old and tested one treatment lotion. It is not a reason to treat an ordinary PHA toner as equivalent to modern first-line acne treatments such as benzoyl peroxide, salicylic acid, or a retinoid.

For your routine, the evidence supports gluconolactone as a useful exfoliating and hydration-supporting ingredient. It does not establish every ingredient sold under the PHA label as equally effective.

How polyhydroxy acid form and formulation affect results

The first question is which PHA or PHA-adjacent ingredient the product actually contains.

Gluconolactone has the clearest direct human evidence. Lactobionic acid is frequently marketed as a PHA but has a different structure and evidence base. A front-label “PHA blend” does not tell you how much of each ingredient is present or whether the blend has been clinically tested.

Concentration is not a quality score. In the small gluconolactone studies comparing 10% and 30%, the higher concentration did not consistently produce better hydration or barrier-related measurements.^[2][3]

pH, leave-on versus rinse-off format, contact time, frequency, solvents, humectants, emollients, and other exfoliating ingredients can all change activity and irritation. A cleanser containing gluconolactone and a leave-on peel should not be expected to behave the same way simply because the ingredient lists overlap.

A PHA product with glycerin, ceramides, panthenol, or other moisturizing ingredients may also feel very different from a thin acid solution at the same headline percentage.

Who may benefit from polyhydroxy acid skincare?

PHA skincare can make sense if you want mild surface exfoliation for roughness or dullness but find stronger acid formulas difficult to tolerate.

It can also be useful when exfoliation and dryness overlap because gluconolactone has human evidence for hydration and barrier-related measurements as well as exfoliating use.

That does not make PHA automatically suitable for sensitive skin. Fragrance, alcohol, other acids, retinoids, low pH, high concentration, or frequent use can still make a finished product irritating.

If clogged pores or acne are the main concern, salicylic acid has a more established modern role. If roughness and dullness already respond well to a tolerated lactic acid or glycolic acid product, there is no reason to switch simply because PHA sounds gentler.

Polyhydroxy acid side effects and irritation risk

PHAs are often marketed as gentle, but irritation is still possible.

A PHA product can cause stinging, redness, dryness, tightness, or peeling depending on the specific acid, concentration, pH, frequency, and complete formula.

The best current cosmetic safety conclusion is ingredient-specific rather than category-wide. In a safety assessment published in 2026, the Expert Panel for Cosmetic Ingredient Safety concluded that gluconolactone is safe in cosmetics under the present practices of use and concentrations described in the assessment. The available data were insufficient for the panel to make the same determination for galactonolactone, glucarolactone, glucoheptonolactone, and ribonolactone.^[6]

Insufficient data do not mean those ingredients are proven unsafe. It means the panel did not have enough evidence to reach a safety conclusion.

If a PHA product causes persistent burning, swelling, severe redness, blistering, or worsening irritation, stop using it rather than assuming a “gentle acid” needs an adjustment period.

How to use polyhydroxy acids in your skincare routine

Follow the directions for the exact product. A cleanser, toner, serum, moisturizer, and peel do not need the same frequency or contact time.

For a leave-on exfoliating product, starting at the lowest frequency allowed by the directions can make it easier to judge tolerance.

If your routine already contains glycolic acid, lactic acid, salicylic acid, retinoids, or another exfoliating treatment, adding a PHA may simply duplicate the same job. More exfoliation is not automatically better.

Use broad-spectrum sunscreen every day. PHA does not replace sun protection, especially when dullness or uneven tone is part of the reason you are exfoliating.

How long do polyhydroxy acids take to work?

A PHA formula may make skin feel smoother or more hydrated fairly quickly, but some of that immediate effect can come from the moisturizing base.

Small gluconolactone studies measured hydration and transepidermal-water-loss changes after several treatments, while the photoaging comparison assessed visible changes over 12 weeks.^[2][3][4]

There is no dependable category-wide timeline because the specific acid, concentration, pH, format, frequency, and concern all vary.

What can you use with polyhydroxy acids?

PHAs fit easily with moisturizing ingredients such as glycerin, ceramides, niacinamide, panthenol, squalane, and other humectants and emollients.

They can also be used in routines containing retinoids, AHAs, or salicylic acid when the overall routine remains comfortable.

Compatibility does not mean you need to layer multiple exfoliants together. If stinging, redness, peeling, or tightness develops, reducing overlapping exfoliation is more useful than relying on PHA’s gentler reputation.

How to choose a polyhydroxy acid product

Start by checking which acid the formula actually contains.

Gluconolactone has the clearest direct human evidence among ingredients commonly marketed under the PHA label. If a brand uses a proprietary PHA complex, look for the underlying INCI ingredients and finished-product testing.

Match the format to the job. A leave-on toner or serum gives more contact time for exfoliation, while a moisturizer may be a better choice when hydration and comfort are the priority.

Do not automatically choose the highest percentage. Small human studies have not shown a simple “more gluconolactone is better” relationship for hydration or barrier measurements.

Be cautious with “safe for all sensitive skin,” “zero irritation,” “acne treatment,” “clinical resurfacing,” or “professional peel results” claims unless the finished product has evidence that supports them.

PHAs alone do not justify Premium pricing. Pay more only when the complete formula offers a meaningful advantage in tolerability, moisturizing support, texture, packaging, or credible finished-product testing.

Do you need a separate polyhydroxy acid product?

Usually, no.

A separate PHA product can make sense when rough texture or dullness remains a real concern and stronger exfoliants have been uncomfortable or unnecessary.

If you already use a well-tolerated AHA, salicylic acid, or retinoid that handles texture well, adding a PHA toner or serum is likely to duplicate an existing step.

PHA is most useful as an alternative, not an obligation. Choose it when its balance of exfoliation, hydration, and tolerability fits your routine better than another approach.

The BB Perspective

Polyhydroxy acids are a useful exfoliating family, but the category is less interchangeable than beauty marketing makes it sound.

Gluconolactone has the strongest direct human evidence, including small studies showing improved hydration and barrier-related measurements and a regimen study suggesting better tolerability than a glycolic-acid routine. That evidence should not be automatically transferred to every ingredient sold under a PHA label.

The best PHA product for you is not necessarily the strongest or most expensive one. It is the formula that gives enough exfoliation to improve roughness or dullness without creating a new irritation problem—and only if your routine actually needs another exfoliating step.

Last reviewed: September 2026