evidently.
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Glycolic Acid (AHA)

GLYCOLIC ACID

The reference exfoliating acid — decades of use and controlled-trial support for texture and tone.

bufferingCAS 79-14-1

Why it works

Glycolic acid, the smallest alpha-hydroxy acid, loosens the bonds between dead surface cells so they shed evenly, revealing smoother skin and diluting surface pigment. At higher concentrations and continued use it also stimulates dermal collagen.

Concentration matters

Leave-on products at 5–10% are the studied home-use range; the classic trial used 8%. Buffered formulas (higher pH) are gentler but slower.

The evidence, by concern

Wrinkles & aging

Good evidence

A classic double-blind trial showed clear improvement at 8%

How sure are we
good
How much it helps
modest but real
Do studies agree
mostly agree

In a 22-week randomized, double-blind, vehicle-controlled trial, 76% of participants using 8% glycolic acid improved in overall photoaging versus 40% on vehicle. Later histology work confirmed real structural changes, not just surface polish.

The receipts

12 trials/reviews indexed · showing most cited

Dark spots

Good evidence

Reliable gradual brightening through exfoliation

How sure are we
good
How much it helps
modest but real
Do studies agree
mostly agree

Controlled trials of glycolic peels and 8–10% creams show improvement in mottled pigmentation over 10–22 weeks — though cream results are less consistent than for texture, and in the classic trial the pigment benefit faded by week 22. Best on surface-level, sun-induced pigment; deeper melasma needs other tools.

The receipts

30 trials/reviews indexed · showing most cited

Safety, without the fear

Anchored to regulatory assessments — not hazard lists. Dose makes the poison; these are the conclusions at real-world cosmetic use.

CIR · Cosmetic Ingredient Review

CIR concluded glycolic acid is safe for consumers at ≤10% and pH ≥3.5, provided the product protects against increased sun sensitivity or directs daily sun protection. Per FDA, AHAs raise sun sensitivity during use and for about a week after stopping — daily sunscreen isn't optional.

Source →
Spotted an error, or a study we missed? Claims were fact-checked against the cited literature in August 2026; independent clinical sign-off is pending — corrections welcome.