Ingredient dossier Nº 035 / The verified record
Polyhydroxy Acids (PHA)
GLUCONOLACTONE
Effective concentration, the pH it needs, how the derivatives compare, stability in the bottle, and the open questions — every scientific claim on this page links to its source.
- gentle exfoliant
- humectant / moisturizing
- antioxidant
- barrier support
- skin conditioning
Editorial verdict / Social intelligence
The gentle acid — if glycolic stings your skin, a PHA gives you most of the smoothing without the burn, plus a hydration-and-antioxidant bonus. 1
- Beauty benefit
- Polyhydroxy acids (PHAs — gluconolactone and lactobionic acid) are the gentle exfoliating acids: they smooth and refine skin like an AHA, but without the sting, which makes them the go-to acid for sensitive, rosacea-prone and easily-irritated skin. As a bonus they're also humectants and antioxidants, so they hydrate and defend while they exfoliate.
- Does it work
- Yes — and they're the sensible choice for anyone whose skin can't take a regular acid. PHAs are a 'next-generation' hydroxy acid built from larger molecules that penetrate more slowly, so they deliver acid benefits without the sensory irritation that limits glycolic or salicylic acid, and they're documented as compatible with clinically sensitive skin, including rosacea. In a 12-week study a gluconolactone (PHA) routine gave anti-aging results comparable to a glycolic-acid one. They also multitask: gluconolactone and lactobionic acid hydrate, provide antioxidant defense, and even support the skin barrier. Honest framing: 'gentle' has a flip side — per use, a PHA is milder and slower than a high-strength glycolic peel, so PHAs are about tolerability and steady results rather than aggressive resurfacing. And they're still exfoliating acids, so daily SPF stays sensible. Vegan. See the science below →
Consensus strength
ModeratePHAs are well-regarded as the gentle, low-irritation exfoliating acids — AHA-comparable benefits without the sting, compatible with sensitive and rosacea-prone skin, with bonus humectant and antioxidant properties. The caveats: 'gentler' means milder/slower than a strong glycolic peel, and much of the foundational evidence comes from the cosmeceutical/developer literature rather than a large independent head-to-head base.
01 / What it does
What it does
Polyhydroxy acids are the gentle, sensitive-skin generation of exfoliating acids. The classic alpha-hydroxy acids (glycolic, lactic) exfoliate and smooth beautifully but can sting and irritate; PHAs — chiefly gluconolactone and lactobionic acid — were developed to deliver similar benefits without that sensory irritation. The trick is molecular size: PHAs are larger molecules than glycolic acid, so they penetrate more slowly and gently, which is exactly why they're tolerated by skin that flares with stronger acids — including rosacea-prone, sensitive and eczema-prone skin. And they multitask: beyond gentle exfoliation, PHAs are humectants that draw in water, antioxidants that help defend against oxidative damage, and barrier-supporters (gluconolactone has even been shown to protect skin's elastin from UV-induced breakdown and to improve barrier function). The honest framing: a PHA is the right call when you want the smoothing, evening benefits of an acid but your skin can't take the sting of an AHA — the trade-off is that gentleness also means a milder, slower effect than a high-strength glycolic peel. PHAs are about tolerability and steady, consistent results, not aggressive resurfacing.
- Review Polyhydroxy acids (PHAs) are a newer generation of AHAs that provide similar effects to alpha-hydroxyacids but do not cause the sensory irritation responses that can limit classical AHA use, and they have been found compatible with clinically sensitive skin, including rosacea. 1
- Review In a 12-week clinical study, a gluconolactone-containing PHA regimen provided antiaging effects comparable to a glycolic-acid (AHA) regimen. 2
- Study Gluconolactone exhibits antioxidant and moisturizing effects, presents soothing effects, protects elastin fibers from UV-induced degradation, and improves the function of the skin barrier. 3
02 / Effective concentration
What percentage actually works
Effective range
Used as leave-on serums/toners
Because PHAs are gentle, they can be used at meaningful strengths without the sting that limits AHAs. Gluconolactone has been evaluated as a 10% and 30% chemical peel, and PHAs appear in everyday serums and toners at lower leave-on levels — the right level depends on whether you want gentle daily smoothing or a stronger periodic exfoliation.
PHAs span the same kinds of formats as other hydroxy acids — daily leave-ons through periodic peels — and their lower irritation potential is the point: a sensitive-skinned user who couldn't tolerate a glycolic product may comfortably use a gluconolactone or lactobionic one. As with any acid, build up gradually and judge by how your skin responds.
- Study Gluconolactone has been evaluated clinically as 10% and 30% chemical peels, illustrating the concentration range used for PHA exfoliation. 3
- Review Hydroxyacids — including the polyhydroxy acids — are used across a wide range of cosmetic and therapeutic formulations, from moisturizers to peels. 4
03 / pH requirement
The pH it needs
Target pH
Acidic, like other exfoliating acids — but notably, PHA acidification of the stratum corneum actually improves barrier function rather than harming it
PHAs work in an acidic environment, as exfoliating acids do. What's distinctive is that re-acidifying the skin's surface is beneficial: lowering stratum-corneum pH with polyhydroxy acids has been shown to improve lipid processing and to inhibit the degradation of corneodesmosomes, supporting barrier structure and cohesion. So unlike a harsh, barrier-disrupting exfoliation, a well-formulated PHA can exfoliate while reinforcing the acidic environment a healthy barrier needs.
- Study Lowering stratum-corneum pH using polyhydroxy acids improved lipid processing and inhibited the degradation of corneodesmosomes, supporting permeability-barrier structure and cohesion. 5
- Review Hydroxy acids — alpha-, beta-, polyhydroxy and bionic acids — act through pH-related and other mechanisms reviewed across their cosmetic and therapeutic applications, with emphasis on their safety and photoactivity. 6
04 / Derivative ladder
How the derivatives compare
Every derivative trades a measure of proven activity for stability or gentleness. Skin conversion is the question that matters — a more stable molecule only helps if your skin can turn it back into the active form.
Polyhydroxy Acids (PHA) has no meaningfully used cosmetic derivative ladder — it is formulated as the free acid itself. That is the form the research below was run on, so there is no conversion step to discount.
05 / Stability & storage
Stability in the bottle
The most useful practical point about PHAs is that they're more than exfoliants: gluconolactone and lactobionic acid are also genuine humectants and antioxidants, so a PHA product tends to hydrate and provide some oxidative-defense benefit alongside its gentle exfoliation. Lactobionic acid in particular is recognized as a cosmeceutical antioxidant that can help protect skin against oxidative injury, and both lactic and lactobionic acids are characterized as strong moisturizing compounds. That multitasking — exfoliate, hydrate, defend — is part of why PHAs suit being used consistently rather than as an occasional aggressive treatment.
- Study Lactobionic acid is a cosmeceutical antioxidant active investigated for protecting the skin against oxidative injury, supporting PHAs' antioxidant (not just exfoliating) role. 7
- Review Alpha-hydroxy and polyhydroxy acids — including lactobionic acid — are valued for their excellent moisturizing and antioxidant properties, making PHAs multitasking humectant-antioxidant exfoliants. 8
In practice Buy it in an opaque, airless, or amber container, store it cool and out of the light, and treat a colour shift toward orange or brown as the signal to replace it — the molecule is telling you it has already oxidised.
06 / How to use it
How to actually use Polyhydroxy Acids (PHA)
- When
- PM (usually) — After cleansing, before moisturizer — start 2–3×/week and build up as your skin tolerates it.
- Pairs well with
- niacinamide, hydrators, ceramides.
- Apply apart from
- strong AHA/BHA (same night), retinoids (same night)(use one in the morning, the other at night — not “never together”)
- What to look for
- A gluconolactone / lactobionic-acid serum or toner (~3–10%) — the gentle acid for skin that stings with glycolic.
- Heads-up
- Gentle and a great pick for sensitive or rosacea-prone skin — but gentler also means milder and slower than a strong AHA. It is still an exfoliating acid, so wear daily SPF; vegan.
Practical guidance for routine placement — not a substitute for a dermatologist’s advice for your skin.
07 / The database
Polyhydroxy Acids (PHA): measured product rankings coming soon
Ranked by $ per gram of active — what the working ingredient actually costs you, not the sticker price. Rows we have reviewed in full link through; the rest are data points from the same crawl.
Buy The INKEY List on Amazon $15.00 Top-ranked pick · affiliate link
No measured products yet — this active's price-per-gram rankings will appear here as products are added.
In the meantime, see how to use Polyhydroxy Acids (PHA) and what to look for on a label .
Contains it, but doesn't disclose a percentage: The INKEY List The INKEY List PHA Toner ; Glow Recipe Glow Recipe Watermelon Glow PHA + BHA Pore-Tight Toner
08 / Safety
Is it safe?
Cosmetic Ingredient Review status
Polyhydroxy acids are widely used cosmetic exfoliants with a favorable tolerability profile; consult the cosmetic-ingredient and clinical literature for specifics.
Gentleness is the headline: PHAs were specifically developed to avoid the stinging and sensory irritation that limit alpha-hydroxy acids, and they're documented as compatible with clinically sensitive skin, including rosacea — which is precisely the audience they serve. That makes them a sensible exfoliating acid for reactive, rosacea-prone or eczema-prone skin that can't tolerate glycolic or salicylic acid. Two honest caveats: they're still hydroxy acids used at acidic pH, so it's wise to wear daily sunscreen and introduce them gradually as with any exfoliant; and the cosmetic forms are synthetic and vegan.
- Review PHAs do not cause the sensory irritation responses that limit classical AHAs and are compatible with clinically sensitive skin, including rosacea, underpinning their gentle safety profile. 1
- Review Reviews of hydroxy-acid applications place special emphasis on their safety and photoactivity, the basis for advising sun protection alongside any exfoliating acid. 6
09 / The limits of the evidence
What we don't know yet
Most of what you read about this ingredient is stated with more certainty than the evidence earns. Here is exactly where the record thins out — so you can weigh the claims above for yourself.
- PHAs are gentle exfoliating acids: the trade-off for low irritation is that, per application, they're milder and slower than a high-strength glycolic peel — they're about tolerability and consistency, not aggressive resurfacing.
- 'PHA' is a class — gluconolactone, lactobionic acid and galactose differ in molecule size and secondary benefits (lactobionic acid, for instance, is a notably strong antioxidant/chelator).
- They're still hydroxy acids used at acidic pH, so daily SPF and gradual introduction remain sensible, even though PHAs are gentler than AHAs.
- Much of the foundational PHA evidence comes from the cosmeceutical/developer literature (the Van Scott–Yu lineage); it's consistent, but the independent, head-to-head evidence base is smaller than glycolic acid's.
- Any 'brightening' from a PHA is the result of gentle exfoliation evening the surface, not a pigment-blocking (tyrosinase-inhibiting) action — it's an exfoliant, not a dedicated brightener. The cosmetic forms are synthetic and vegan.
10 / What people say
What formulators and users say
What works
-
A new generation of AHAs, called polyhydroxy acids (PHAs), was discovered that provide similar effects as AHAs but do not cause the sensory irritation responses that can limit the use of classical AHAs. PHAs have been found to be compatible with clinically sensitive skin, including rosa review
- Common Real anti-aging results — comparable to a glycolic-acid regimen in a clinical study 2
This 12-week clinical study evaluated gluconolactone-containing products (PHAs) in comparison with glycolic acid-containing products (AHAs). review
-
Gluconolactone (GLA) exhibits antioxidant and moisturizing effects. It also presents soothing effects, protects elastin fibers from UV-induced degradation, and improves the function of the skin barrier. Study
What to know
- Common 'Gentler' means milder and slower — a PHA won't resurface like a high-strength glycolic peel 1
provide similar effects as AHAs but do not cause the sensory irritation responses that can limit the use of classical AHAs review
- Some Still an exfoliating acid — wear daily SPF; and 'PHA' is a class, so gluconolactone vs lactobionic differ 87
Special emphasis is devoted to the saf review
What you'd only know from the reviews
-
A PHA doesn't just spare the barrier — it can actually help it. Re-acidifying the skin surface with polyhydroxy acids has been shown to improve the skin's lipid processing and to stop the breakdown of the corneodesmosomes that hold the stratum corneum together — the opposite of a harsh, barrier-stripping exfoliation. That's a big part of why PHAs feel kind to skin that flares with stronger acids: the exfoliation comes with barrier support rather than barrier damage. 4
-
Think of PHA as an exfoliant that also moisturizes. Lactobionic and lactic acids are characterized as strong moisturizing compounds, and lactobionic acid doubles as a cosmeceutical antioxidant — so unlike a bare glycolic solution, a PHA tends to hydrate and provide oxidative defense alongside its gentle smoothing. Just remember 'PHA' is a class: gluconolactone, lactobionic acid and galactose differ a little in size and secondary benefits, so check which one a product actually uses. Vegan. 6
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
11 / Questions
Frequently asked
- What is a PHA, and how is it different from an AHA?
- PHA stands for polyhydroxy acid — chiefly gluconolactone and lactobionic acid. They're a gentler generation of exfoliating acids: chemically related to alpha-hydroxy acids (like glycolic) but built from larger molecules that penetrate more slowly, so they smooth and exfoliate with far less stinging and irritation. They also double as humectants and antioxidants, which AHAs generally don't. 12
- Is a PHA actually as effective as an AHA?
- For everyday smoothing and anti-aging, surprisingly close — a 12-week study found a gluconolactone (PHA) regimen gave anti-aging effects comparable to a glycolic-acid (AHA) one, but with less irritation. The honest caveat is that 'gentler' does mean milder per application: if you want aggressive resurfacing of stubborn texture or pigmentation, a high-strength AHA still goes further. PHAs win on tolerability and consistency. 21
- Is PHA good for sensitive or rosacea-prone skin?
- Yes — that's its entire reason for existing. PHAs were designed to deliver acid benefits without the sensory irritation that limits AHAs, and they're documented as compatible with clinically sensitive skin, including rosacea. If glycolic or salicylic acid stings or flares your skin, a gluconolactone or lactobionic PHA is the gentle alternative to try. 1
- Do PHAs do anything besides exfoliate?
- Yes, and it's a real advantage. Gluconolactone and lactobionic acid are humectants (they draw in water) and antioxidants (they help defend against oxidative damage), and gluconolactone has been shown to protect skin's elastin from UV-induced breakdown and to improve barrier function. So a PHA tends to exfoliate, hydrate and provide some antioxidant support at once. 37
- Do I still need sunscreen with a PHA?
- Yes. PHAs are gentler and are even noted to support the skin barrier, but they're still exfoliating acids used at an acidic pH, and the hydroxy-acid literature emphasizes photoactivity and safety. Daily sunscreen is sensible with any exfoliating acid — and it protects the smoother, fresher skin you're working to reveal. 6
12 / References
Sources
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8