Alpha hydroxy acid (AHA)
Lactic Acid
INCI: Lactic Acid·Studied at 5–12% (leave-on)·Moderate evidence
A larger, milder alpha hydroxy acid than glycolic that also acts as a natural moisturising factor, studied for the appearance of a smoother, brighter surface with more hydration and less sting.
Studied for
- ·The appearance of a smoother, more even surface
- ·The look of brighter, more even tone
- ·The appearance of hydrated, less rough-looking skin
How it’s thought to work
Loosens the bonds between surface skin cells like other AHAs, and its larger molecule penetrates more slowly, which is studied for a gentler feel; it raises sun sensitivity, so daytime sunscreen matters.
Layering note
Often kept apart from: retinoids in the same layer for sensitive skin.
Questions
- Is lactic acid gentler than glycolic acid?
- Usually, yes. Lactic acid is a larger molecule that gets into skin more slowly, so it tends to feel milder, and it doubles as a humectant. It still raises sun sensitivity, so daily sunscreen is part of using it.