Gl
Glycolic Acid
Glycolic AcidExfoliant
Smallest alpha hydroxy acid. Penetrates well — strong exfoliation, comparatively higher irritation.
What it does
Glycolic acid breaks the bonds holding dead surface cells together, smoothing texture and improving tone over weeks. Smaller molecule = deeper penetration vs. lactic or mandelic. OTC products typically 5–10%; in-office peels are higher.
The evidence, graded
expert consensusRetinol and AHAs (glycolic, lactic) can both irritate skin when layered in the same routine. Most people do better alternating them on different nights.Mukherjee 2006 · Clinical Interventions in Aging ↗
expert consensusTretinoin is significantly more potent than retinol; combining it with AHAs in the same routine raises irritation risk substantially.Mukherjee 2006 · Clinical Interventions in Aging ↗
expert consensusAHAs and BHAs can be combined safely in well-formulated products. The 'never mix them' rule is overstated — the real concern is total acid load on the skin barrier, not the chemistry of mixing them.Kornhauser 2010 · Clinical and Cosmetic Investigative Dermatology ↗
expert consensusHigh-percent AHAs (above 10%), strong retinoids, and aggressive professional treatments are usually unnecessary before 25 unless treating a specific condition. This is clinical convention, not a safety claim — they're not unsafe, just not indicated for cosmetic prevention in young skin.Hughes 2013 · Annals of Internal Medicine ↗
emergingAlpha arbutin is pH-flexible and works alongside AHAs without efficacy loss. The AHA's mild exfoliation can enhance arbutin penetration into the targeted melanocyte layer.Maeda 1996 · Journal of Pharmacology and Experimental Therapeutics ↗
Graded per the methodology: strong · moderate · emerging · expert consensus. A weak source on a strong claim gets the weaker label.
Pairs worth knowing
Read more
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