Ingredient · Alpha-hydroxy Acid · Glycolic
P. 09 · BRIEFThe most-studied alpha-hydroxy acid in dermatology. Smallest molecule, deepest penetration, strongest evidence on tone and texture — and the steepest irritation curve to match. The default home AHA when used at a sensible dose, the workhorse of in-clinic peels at higher ones.
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Glycolic acid is the smallest alpha-hydroxy acid by molecular weight, derived originally from sugarcane. Its size lets it move past the corneocyte surface and reach the lower stratum corneum and viable epidermis — which is why it produces the most visible AHA result and the most predictable AHA irritation. There is no separating those two facts.
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On exfoliation
Cleaves corneodesmosomes between stratum-corneum cells. Visible smoother texture within 2 weeks.
On the dermis
Stimulates fibroblast proliferation and dermal glycosaminoglycan synthesis at sustained use.
On pigment
Accelerates turnover of pigmented keratinocytes; useful adjunct for PIH but not first-line for melasma.
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Twice weekly to start. Most home users live here.
Nightly or alternate nights. Plateau dose for home use.
For experienced skin only. Rising irritation, marginal benefit.
In-clinic only. Procedural risk profile.
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The reference beginner AHA. Honest pH, gentle vehicle.
Cheap, effective, drying for some. Skip the package warning at your peril.
Mixed-acid premium product. Good vehicle, premium markup.
The cult classic. 12 weeks in, the texture difference is undeniable.
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Glycolic for established users wanting maximum exfoliation. Lactic for sensitive skin or anyone who also wants hydration. Different tools for adjacent jobs.
Twice weekly to start; build to nightly only if your barrier tolerates it. The 'every night' pitch on the bottle is aspirational, not prescriptive.
Yes, more than usual. AHAs measurably increase UV-induced damage for up to a week. Skip sunscreen and you have actively made things worse.
Adjunct only. Tranexamic acid, hydroquinone, and azelaic are first-line. Use glycolic to support turnover, not to drive the result.
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— Cross-references