AHA (glycolic / lactic acid)

AHA · alpha hydroxy acids · glycolic acid · lactic acid

Alpha-hydroxy acids for smoother texture, brighter tone and the look of fine lines.

TypeCosmetic (topical)

The grade answers: What does the human evidence support for: Exfoliation, texture & tone?

Grade

Moderate

The grade rates evidence quality — it is not advice to take or buy.

Class: Skincare / topical
Primary use: Exfoliation, texture & tone
Evidence strength: medium
Last reviewed: 2026-07-01

Bottom line

Well-evidenced cosmetic exfoliants: at sensible strengths they smooth texture and even tone, and lactic acid is the gentler, more hydrating option. Overdoing strength or frequency is where they go wrong.

What the evidence says

AHAs like glycolic and lactic acid have controlled evidence for improving skin texture, tone and the appearance of fine lines and photoaging through exfoliation and, over time, effects in the dermis. Glycolic (smallest molecule) penetrates most and is the most studied; lactic acid is gentler and also humectant. This describes cosmetic exfoliation, not chemical peels performed as medical procedures. As always the ingredient's evidence isn't a specific product's promise — concentration, pH and formulation drive both benefit and irritation. Grade B.

Key studies

[1]
Alpha-hydroxy acids and photoaging / texture · RCT
Improved texture and tone with regular use.
Open on PubMed ↗
[2]
Lactic acid on skin (gentler AHA) · review
Gentler, also humectant.
Open on PubMed ↗
[3]
AHA mechanisms and dermal effects (review) · review
Surface and deeper effects over time.
Open on PubMed ↗

See all studies on PubMed ↗

Scoped PubMed search, not a curated bibliography: the individual PMIDs for this entry have not yet been verified one by one. For that reason it is not used to support a high grade and is awaiting review.

Mechanism

Weaken the bonds between surface corneocytes to promote even shedding, smoothing texture and tone; chronic use is associated with increased dermal glycosaminoglycans and collagen in studies.

Safety

Cause dose-dependent stinging, irritation and increased sun sensitivity — daily SPF is important. Start low and infrequent. High-strength professional peels are a separate, clinical matter and out of scope here.

Dosage context

Leave-on cosmetic products commonly use ~5–10% at a controlled pH; higher strengths and low pH raise both efficacy and irritation. More is not better if it inflames the skin.

Examples of application

Used a few evenings a week, per the product's instructions.
Followed by daily sunscreen, since AHAs raise sun sensitivity.
Lactic acid for sensitive skin; start low and infrequent.

From the field

AHAs work — the mistakes are strength and frequency, not the ingredient. We grade them B, favour gentler lactic acid for sensitive skin, and always pair with sunscreen.

Related molecules

PHA (lactobionic acid)C Retinoids (retinol)B Sun protection (SPF)A

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