Skin Actives

Polyhydroxy Acids (PHAs)

Also known as: PHA, Gluconolactone, Lactobionic acid, Galactose

The gentle exfoliators — polyhydroxy acids deliver AHA-like renewal without the sting, built for sensitive and rosacea-prone skin.

By IngredientWiki Editorial Team
Fact-checked by IngredientWiki Editorial Team
Updated 2026-09-26
2 min read

In short

Polyhydroxy acids (PHAs) are a family of larger, slower-acting chemical exfoliants — mainly gluconolactone, lactobionic acid, and galactose — designed to fix the alpha hydroxy acid (AHA) problem: glycolic acid works well but stings, and sensitive skin often cannot tolerate it. Because PHA molecules are bigger, they penetrate the stratum corneum more slowly and surface-concentrated, exfoliating dead cells with far less irritation, while doubling as humectants that attract water. They do not match glycolic acid's raw speed, but for sensitive, rosacea-prone, or over-exfoliated skin, they are the sustainable option.

Larger molecules than AHAs — slower, surface-level exfoliation
Much less stinging than glycolic acid; safe for sensitive skin
Also humectants — hydrate while they exfoliate
Main PHAs: gluconolactone, lactobionic acid, galactose

What is Polyhydroxy Acids (PHAs)?

The exfoliating acid market spent years convincing consumers that effectiveness equals sting. Polyhydroxy acids are the correction to that equation. Developed from the same chemistry lineage as glycolic acid, PHAs trade raw potency for tolerability: a larger molecule that works at the skin's surface, loosening the bonds between dead cells while pulling in moisture and, in some studies, supporting barrier function. They have become the default recommendation for skin that flinches at AHAs — sensitive, rosacea-prone, and post-treatment skin included.

Where it comes from

Natural sources

Gluconolactone — oxidized form of glucose
Lactobionic acid — oxidized lactose (milk sugar)
Galactose — a natural sugar

How it's made

Produced from sugars for cosmetic use; first popularized as gluconolactone in clinical formulations.

What it does in products

Benefits

Gentle exfoliation and smoother texture

strong evidence

Clinical studies show PHAs improve skin smoothness, texture, and radiance comparable to AHAs over time, with significantly lower stinging and irritation scores.

Sensitive and rosacea-prone skin tolerance

moderate evidence

The defining advantage: PHAs are well tolerated by skin types that cannot use glycolic acid, including rosacea and atopic-prone skin, with slower but steady renewal.

Hydration support

moderate evidence

PHA molecules bind water like humectants, so exfoliation arrives with a hydration benefit — the opposite of the dry tightness AHAs can cause.

Anti-aging maintenance

emerging evidence

Regular PHA use supports collagen-friendly signaling and surface renewal; fine-line improvement is gradual and best viewed as long-term maintenance.

Side effects & safety

Mild stinging at high concentrations (uncommon)Far less than AHAs, but 15%+ products can still tingle on compromised skin.

Initial adjustment flaking (uncommon)Mild and transient as dead-cell buildup releases.

Safety considerations

Topical PHAs are generally considered safe in pregnancy at typical cosmetic concentrations.
Combine cautiously with retinoids and other acids; though gentler, PHAs still exfoliate.
Not for: Known allergy to the specific PHA

How it's used

In skincare

Typical use: 5–15% in toners, serums, and creams. Start 2–3 nights weekly, building toward daily use as tolerated. Unlike AHAs, PHAs pair reasonably with daytime use in gentle formulas — but sunscreen remains essential.

Regulatory status

Approved cosmetic ingredients; not drugs.
INCI name on cosmetic labels: Gluconolactone (or Lactobionic Acid / Galactose).
CIR reviewed gluconolactone and lactobionic acid as safe in cosmetics.

PHA vs AHA vs BHA: picking your exfoliant

The three acid families differ in size, solubility, and targets. AHAs like glycolic acid are small, water-soluble, and potent — the classic resurfacing choice for resilient skin. BHAs like salicylic acid are oil-soluble and penetrate pores — the acne-prone skin's pick. PHAs are the largest and gentlest, staying at the surface where they polish without provoking, which suits sensitive, rosacea-prone, and easily irritated skin. Many modern toners blend them (PHA + BHA), letting formulators tune gentleness and pore action together. If an AHA serum leaves you red, the problem is usually the AHA — not exfoliation itself.

Frequently asked questions

Are PHAs as effective as AHAs?

Comparable in texture and radiance benefits over a longer timeline — studies find similar smoothing outcomes with much less irritation. If your skin tolerates glycolic acid, it is faster; if not, PHAs deliver the renewal without the redness.

How often should I use PHA exfoliants?

Start 2–3 nights per week and build toward daily use as tolerated. Gentle toners can often be used daily; higher-strength serums suit alternate nights.

Can I use PHAs with retinol?

Yes, and PHAs are often the recommended acid partner for retinoid users because of their low irritation potential. Introduce one product at a time and monitor for any flaking.

The bottom line

Polyhydroxy acids solve the exfoliation dilemma for sensitive skin: real renewal, hydration built in, and irritation measured in fractions of an AHA's. Slower than glycolic acid, yes — but sustainable, which in skincare usually wins.

References

Polyhydroxy acids and skin tolerance — literature search. PubMed (National Library of Medicine). https://pubmed.ncbi.nlm.nih.gov/?term=polyhydroxy+acids+skin+gluconolactone
Gluconolactone and sensitive skin — literature search. PubMed (National Library of Medicine). https://pubmed.ncbi.nlm.nih.gov/?term=gluconolactone+sensitive+skin
Lactobionic acid and skin — literature search. PubMed (National Library of Medicine). https://pubmed.ncbi.nlm.nih.gov/?term=lactobionic+acid+skin
Gluconolactone compound summary. PubChem (National Library of Medicine). https://pubchem.ncbi.nlm.nih.gov/compound/92280