Glycolic Acid: AHA Concentration and pH Limits to Watch

Glycolic acid formulas are one of the clearer examples of why two numbers matter more than one. Everyone fixates on the percentage on the bottle, "10% glycolic," "20% glycolic," but percentage alone doesn't tell you nearly as much as percentage combined with pH.

The basics: naming and identity

Glycolic acid's INCI name is simply Glycolic Acid, and its CAS number is 79-14-1. It's the smallest alpha hydroxy acid, derived originally from sugarcane though now largely produced synthetically, and it's prized in skincare because its small molecular size lets it penetrate skin more readily than some of the larger AHAs like lactic or citric acid. That penetration is exactly why concentration and pH both matter so much here.

Why percentage alone is misleading

A 10% glycolic acid product formulated at a low pH can be considerably more active, and more irritating, than a 15% product formulated at a higher pH. That's because AHAs work through their free acid form, and the proportion of glycolic acid that exists as free, unbuffered acid versus its neutralized salt form depends heavily on pH. A formula can be buffered, partially neutralized, or blended with other ingredients in a way that changes its real-world exfoliating strength independent of the raw percentage listed.

This is why regulatory attention to AHA products tends to look at concentration and pH together, not concentration in isolation. A product's actual free acid content and its pH jointly determine how it behaves on skin, and by extension, how it should be classified and what claims are appropriate for it.

Home use versus professional use

Glycolic acid products marketed for daily home use are generally formulated at gentler concentrations and higher pH than the stronger peel-strength formulas used in professional treatments. This split matters for a few reasons:

• Professional-strength peels at high concentration and low pH are a meaningfully different risk category than a daily home lotion, and the claims, labeling, and sometimes the regulatory classification around them reflect that.
• Home-use products still need accurate concentration reporting, since "up to 10%" marketing language on a label doesn't excuse imprecise concentration data on your actual notification.
• The exact concentration and pH thresholds that separate categories, and any specific limits that apply, are the kind of detail worth confirming against current guidance directly rather than relying on a number from an old formulation note, since these thresholds are the sort of thing that can be refined over time.

What to document before you file

If you're formulating a glycolic acid product, a few pieces of documentation make your Cosmetic Notification Form both accurate and easy to defend later:

1. The actual glycolic acid concentration in the finished product, not just what your raw material supplier's percentage was before dilution into the full formula.
2. The finished product's pH, measured directly rather than assumed from the formula's theoretical composition.
3. Whether the product is buffered or partially neutralized, since a partial neutralization changes the free acid available even at a fixed nominal percentage.
4. Your intended use category, home use or professional application, since this shapes appropriate labeling and use instructions.

A simple reference table

Factor	Why it matters
Nominal glycolic acid %	Starting point, but incomplete on its own
Finished product pH	Determines how much is active free acid
Buffering/neutralization	Changes effective strength at a fixed percentage
Home vs professional use	Different formulation norms and claims

Claims worth a second look

Glycolic acid products often carry claims like "exfoliates," "smooths texture," or "brightens," which sit comfortably as cosmetic claims. Claims that veer into treating a skin condition, clearing acne scarring, or resurfacing in a way that reads as therapeutic rather than cosmetic, are worth reviewing carefully, since that kind of language can push a product toward drug-type claims territory rather than staying within standard cosmetic notification.

Getting the concentration and pH data right isn't just a filing formality, it's the information that actually describes what your product does on skin. Cosmetic Comply's ingredient matching pulls the correct INCI name and CAS number for ingredients like glycolic acid automatically and flags concentration-sensitive entries for a closer look from a real reviewer, which is particularly useful for AHA formulas where the percentage on its own never tells the whole story.