PHA Exfoliant for Sensitive Skin: Gluconolactone, Lactobionic Acid and How They Work

A PHA exfoliant is usually the best acid for sensitive skin. Polyhydroxy acids such as gluconolactone and lactobionic acid have larger molecules than glycolic acid, so they penetrate slowly and stay near the surface, exfoliating gently while drawing water into the skin. In a 12-week study, a PHA regimen matched most of an AHA regimen's anti-aging results with less stinging and burning.

Below we explain what PHAs are, why their size makes them gentler, how they compare with AHAs and BHA, who they suit (sensitive and reactive skin, rosacea-prone skin, people on retinoids) and, just as important, what they can't do.

What are PHAs?

PHAs, or polyhydroxy acids, are a newer generation of alpha hydroxy acids that carry several hydroxyl groups instead of one. A review of hydroxy acids in Clinical, Cosmetic and Investigational Dermatology describes them as carboxylic acids with two or more hydroxyl groups that give effects similar to AHAs with less irritation. Attaching a sugar molecule to a PHA gives a bionic acid; lactobionic acid is the best known.

On ingredient lists you'll usually see:

• Gluconolactone: the review calls it the most popular PHA marketed today.
• Lactobionic acid: a bionic acid derived from lactose, according to a 2026 review of hydroxy acids.

Because PHAs are technically AHAs, researchers describe them as the next generation of AHAs. Products often pair them with other acids, so read the full list to see what else you're getting.

What is gluconolactone, and why is it gentler?

Gluconolactone is a PHA whose larger, water-loving molecule moves into skin slowly, so it exfoliates mildly at the surface. Its molecular weight is about 178 daltons, and lactobionic acid's is about 358 daltons, compared with roughly 76 daltons for glycolic acid. Size matters here. Cleveland Clinic explains that glycolic acid's small size lets it penetrate the skin more easily than other acids, which is part of why it can irritate.

The 2026 review describes lactobionic acid's penetration as shallow and slow due to high molecular weight, acting mainly on the surface to strengthen the barrier. It adds that this exfoliation is superficial and significantly milder than AHAs or BHAs, avoiding immediate visible peeling even in sensitive skin, thanks to the molecule's size, extreme affinity for water and humectant properties.

What are the benefits of polyhydroxy acids?

PHAs offer gentle smoothing plus hydration, antioxidant effects and barrier support. Here's what the evidence says, and how strong it is.

• Exfoliation and smoothing. Reviews describe anti-aging and skin-smoothing effects comparable to AHAs.
• Hydration. PHAs function as humectants and moisturizers. A literature review found that lactic and lactobionic acids bind large amounts of water and help maintain the epidermal barrier, making them options for sensitive skin, including skin with visible broken capillaries.
• Antioxidant activity. Most PHAs have antioxidant properties, and bionic acids inhibit matrix metalloproteinase enzymes, an effect the Green review links to a preventive anti-aging benefit.
• Barrier support. PHAs can enhance stratum corneum barrier function, making skin more resistant to chemical irritation. In a mouse study, lactobionic acid and gluconolactone lowered skin surface pH and improved barrier recovery; that is animal data, so treat it as supporting evidence.

Much of the early PHA research came from scientists at a skin care company: the author affiliations on the Edison and Green papers list NeoStrata. The results are consistent, but independent trials are fewer.

PHA vs AHA vs BHA: how do they compare?

PHAs are the slowest and gentlest of the three, AHAs work faster on the surface, and BHA is the one that reaches into oily pores.

The head-to-head evidence comes from a 12-week study comparing gluconolactone products with glycolic acid products. Both regimens showed significant anti-aging benefits. The AHA did better on two measures at week 12: sallowness improved 17.1% versus 12.4%, and skin resilience (pinch recoil) 13.5% versus 10.2%. The PHA regimen was better tolerated, with stinging and burning significantly worse in the AHA group at weeks 6 and 12. The molecule-size figures in the table come from PubChem, including about 138 daltons for salicylic acid, and match the 2026 review for glycolic acid. For the AHA and BHA side of things in more depth, see AHA vs BHA.

Who should use a PHA exfoliant?

PHAs are best suited to people whose skin reacts to regular acids. The Green review says the newer polyhydroxy and bionic acids offer the benefits of AHAs without irritation, making them suitable for sensitive skin, rosacea and use after cosmetic procedures.

Sensitive and reactive skin

If glycolic acid stings you, a PHA is the obvious next try. The Grimes review reports PHAs were compatible with clinically sensitive skin, including rosacea and atopic dermatitis. Pair it with a short, fragrance-free routine; our sensitive skin routine guide lays one out.

Rosacea-prone skin

The research is encouraging, but talk to a dermatologist before adding any acid. One study evaluated a PHA skin care regimen combined with azelaic acid 15% gel in rosacea patients. A 2025 study of 200 people with mild rosacea redness compared a serum containing 5% gluconolactone and 1% lactobionic acid, used for 30 days, with a single intense pulsed light session; both improved redness, but the light treatment did more for redness and overall appearance. Meanwhile, the AAD's rosacea tips advise avoiding glycolic and lactic acid and say that if you exfoliate, you should stop. Taken together: a PHA may be tolerable for some people with rosacea, but it's a decision to make with a dermatologist, ideally as part of a treatment plan. Our guide to rosacea triggers can help you track what sets yours off.

People already using a retinoid

PHAs are one of the few acids that have been studied alongside retinoids. The Grimes review reports PHA products used with retinoic acid for adult acne were well tolerated. Still, the AAD warns that exfoliating while using retinoids or retinol can worsen dryness, so let your skin settle on the retinoid first, then add a PHA on non-retinoid nights. If you're just starting a retinoid, see retinol for beginners.

Deeper skin tones

PHA products were found compatible with African American, Caucasian, and Hispanic/Asian skin in the studies the Grimes review summarizes. This matters because the AAD warns that aggressive exfoliation can lead to dark spots on darker skin tones, so a gentle acid is a sensible place to start.

What can't PHAs do?

PHAs are a poor fit for blackheads, and they work more slowly than AHAs on dullness and firmness. The 2026 review suggests that lactobionic acid's strong affinity for water likely limits how far it gets into oily pores, which is where salicylic acid shines. In the 12-week comparison, glycolic acid did better on sallowness and skin resilience. And gentle doesn't mean reaction-free: the same 2026 review lists occasional mild itching, burning or redness in sensitive people.

If your main goal is clearing clogged pores or fading stubborn sun damage, a PHA alone may feel underwhelming. Some people use a PHA most nights and keep a stronger acid for a once-a-week treatment, if their skin allows.

How do you use a PHA?

Introduce a PHA like any other acid: one product, a few evenings a week, building up if your skin stays calm.

1. Choose the format. PHAs show up in cleansers, toners, serums and moisturizers. A leave-on toner or serum does the most; a cleanser is the mildest start.
2. Start two or three evenings a week. Apply after cleansing, follow with moisturizer.
3. Increase slowly. Move toward the frequency on the label only if you have no redness, stinging or flaking.
4. Wear sunscreen every morning.

Do PHAs increase sun sensitivity? The evidence is reassuring, though small. In a one-month study cited by the Kornhauser review, skin treated with 8% glycolic acid showed a significant increase in sunburn cells, while skin treated with 8% gluconolactone did not; it involved only 11 volunteers. Since PHAs are part of the AHA family and the FDA advises sun protection when using AHAs, keep up daily SPF anyway. If you're pregnant or breastfeeding, ask your doctor or midwife before starting any new acid.

Stop and see a dermatologist if you get swelling, blistering, or redness and burning that doesn't fade after you stop the product.

How can a selfie scan or ingredient scanner help?

Gentle acids change skin slowly, so a consistent record helps you decide whether a PHA is doing anything. Pori gives each selfie an overall skin score with a breakdown that includes Hydration & Moisture and Pores & Texture, which you can compare week to week. Its ingredient scanner (part of Pro) reads a barcode or a photo of the label and flags each ingredient as beneficial, use with caution or avoid for your skin type, which is handy when a "gentle" product also contains glycolic acid or fragrance.

An app reads your skin's appearance, and an app is not a diagnosis. For rosacea, eczema or any rash, a dermatologist should guide treatment.