What percentage of PHA actually works?

PHAs are chemically related to alpha-hydroxy acids but built from larger molecules, which means they penetrate the skin more slowly. That slower penetration is exactly why PHAs don't trigger the sensory irritation (stinging, burning) that limits how high a formulator can push glycolic or lactic acid — and it's why gluconolactone can be tested at concentrations, like 30%, that would be aggressive for a classic AHA. PHAs also do double duty: acidifying the stratum corneum with a polyhydroxy acid has been shown to improve lipid processing and inhibit degradation of corneodesmosomes, meaning the same acidic environment that exfoliates also supports barrier cohesion — a mechanism distinct from a harsher, barrier-disrupting peel.

• 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 have been found compatible with clinically sensitive skin, including rosacea. ¹
• Study Lowering stratum-corneum pH using polyhydroxy acids improved lipid processing and inhibited the degradation of corneodesmosomes, supporting permeability-barrier structure and cohesion. ⁴

The clearest percentage-specific clinical data for a PHA comes from a study evaluating gluconolactone chemical peels at 10% and 30%, measuring their effects on skin sebum production, surface pH, and transepidermal water loss (TEWL). Both concentrations produced measurable changes on these objective skin parameters, consistent with gluconolactone's dual identity as an exfoliant and a barrier-supporting humectant/antioxidant rather than a purely aggressive resurfacing agent. This is the kind of direct, stated-percentage data that's rare in the PHA literature — most gluconolactone and lactobionic acid research either doesn't specify a percentage or tests a finished multi-ingredient product.

• Study Gluconolactone chemical peels were evaluated at 10% and 30% concentrations for their effects on sebum production, surface pH, and transepidermal water loss (TEWL). ³

Outside of the peel-strength data, the most cited PHA efficacy claim comes from a 12-week clinical study that found a gluconolactone-based skin care regimen provided antiaging effects comparable to an alpha-hydroxy-acid (glycolic) regimen, with less irritation reported for the PHA arm. This is genuinely useful, practically relevant evidence — it's the study behind the 'PHA works about as well as AHA, gentler' claim repeated across skincare media. The honest gap: the published record of this study doesn't state the specific gluconolactone percentage used in the daily leave-on regimen, so it can't be cited as a specific-percentage data point the way the 10%/30% peel study can. Treat it as strong support for PHA daily-use products generally, not as evidence for any particular leave-on percentage.

• Review In a 12-week clinical study, a gluconolactone-containing PHA regimen provided antiaging effects comparable to a glycolic-acid (AHA) regimen. ²

One honest caveat The published summary of this 12-week regimen study does not state the specific gluconolactone leave-on percentage used. It supports PHA daily-use efficacy generally, not a specific percentage claim.

Gluconolactone appears in leave-on serums and toners — for example, it's part of the formula in Maelove's Glow Maker vitamin C serum, where it's included alongside the antioxidant actives rather than as a standalone exfoliating peel. Most leave-on PHA products don't disclose their gluconolactone percentage, which is consistent with the broader gap noted above: the 10%/30% data comes from in-office or at-home peel studies, not from a published minimum-effective percentage for everyday leave-on use.

What percentage of PHA is effective?

The clearest data is from a peel study testing gluconolactone at 10% and 30%, both of which produced measurable changes in sebum, surface pH, and TEWL (PMID:37335807). For daily leave-on products, a 12-week gluconolactone regimen matched a glycolic-acid regimen for anti-aging effects (PMID:15002657), but that study didn't publish the specific percentage used in the leave-on formula, so there's no confirmed 'minimum effective %' for everyday PHA serums and toners. ³²

Is 30% PHA too strong for home use?

30% gluconolactone has been studied as a chemical peel, which implies a more controlled, often in-office or periodic-use context rather than an everyday leave-on product. Because PHAs are gentler than AHAs at a given percentage, a 30% PHA peel is not equivalent in irritation potential to a 30% AHA peel — but 'gentler' doesn't mean 'no different from a lower strength.' Follow product-specific instructions and build up gradually with any higher-percentage exfoliating acid. ³¹

Is PHA as effective as AHA?

For everyday smoothing and anti-aging effects, a 12-week study found a gluconolactone (PHA) regimen delivered results comparable to a glycolic-acid (AHA) regimen, with less irritation (PMID:15002657). The honest caveat: 'comparable at everyday use levels' doesn't mean identical at every concentration — for aggressive resurfacing of stubborn texture, a high-strength AHA still has more independent peel data behind it. ²

Why don't PHA serums list a percentage the way vitamin C or niacinamide products do?

Most don't disclose it, and the published PHA literature reflects the same gap — the strongest percentage-specific data (10%/30%) comes from peel studies, not from leave-on serum research. A product like Maelove's Glow Maker includes gluconolactone in its formula without listing a specific percentage, which is standard practice for this ingredient class rather than something unique to one brand.

Is PHA safe for sensitive or rosacea-prone skin at these percentages?

PHAs were specifically developed to avoid the sensory irritation that limits classical AHAs, and are documented as compatible with clinically sensitive skin, including rosacea (PMID:15002656). That tolerability profile is a key reason PHAs can be studied and used at higher percentages (like the 30% peel) than a comparable AHA product would attempt. Still, any acid at a higher percentage warrants gradual introduction and daily SPF. ¹

1. 1

   The use of polyhydroxy acids (PHAs) in photoaged skin

   Grimes PE, Green BA, Wildnauer RH, et al · Cutis 73(2 Suppl):3-13 · 2004

2. 2

   A polyhydroxy acid skin care regimen provides antiaging effects comparable to an alpha-hydroxyacid regimen

   Edison BL, Green BA, Wildnauer RH, et al · Cutis 73(2 Suppl):14-7 · 2004

3. 3

   Evaluation of the effects of 10% and 30% gluconolactone chemical peel on sebum, pH, and TEWL

   Jarzabek-Perz S, Dziedzic M, Rotsztejn H, et al · J Cosmet Dermatol 22(12):3305-3312 · 2023

4. 4

   Acute acidification of stratum corneum membrane domains using polyhydroxyl acids improves lipid processing and inhibits degradation of corneodesmosomes

   Hachem JP, Roelandt T, Schurer N, et al · J Invest Dermatol 130(2):500-10 · 2010