L-lactic acid is a naturally occurring alpha hydroxy acid used to exfoliate the skin by loosening the bonds between corneocytes, promoting cell turnover. At lower concentrations it also acts as a humectant, helping to hydrate and improve skin texture, tone, and barrier function.
| Reported effect | How often | Notes |
|---|---|---|
Stinging or burning sensation on application | Common | Transient, especially at higher concentrations or on compromised skin. |
Mild erythema (redness) | Common | Usually temporary and resolves shortly after use. |
Dryness or flaking | Common | Related to increased exfoliation, particularly when starting use. |
Increased photosensitivity | Common | AHAs can heighten UV sensitivity; daily sunscreen is advised. |
Irritant contact dermatitis | Uncommon | More likely with high concentrations, low pH, or frequent application. |
Post-inflammatory hyperpigmentation | Uncommon | More common in darker skin types after irritation or overuse. |
Allergic contact dermatitis | Rare | True allergy to lactic acid is uncommon but documented. |
Chemical burn or blistering | Rare | Associated with very high concentrations or misuse of peel products. |
Frequencies reflect typical cosmetic use reported in the literature, not a guarantee for your skin.
Peer-reviewed papers on this ingredient, via PubMed.