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
B
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]
- [3]
AHA mechanisms and dermal effects (review) · review
Surface and deeper effects over time.
Open on PubMed ↗
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.