Lactic Acid (AHA)
INCI: Lactic Acid
Lactic acid is an AHA with a larger molecule than glycolic acid, so it penetrates more gently — it exfoliates and improves texture with less irritation risk, which makes it a reasonable entry point into AHAs for sensitive or beginner skin.
How to introduce it
2x
Starting / week
4x
Target / week
4w
Ramp period
8w
Fair to judge by
Possible purging window: weeks 1–3 — temporary increased breakouts as turnover speeds up. Don't stop or judge the ingredient during this window.
Rules that don't bend
- Patch test 48 hours before first facial use.
- Sunscreen is mandatory every morning an AHA was used the night before.
- Never combine with retinoids or benzoyl peroxide in the same session.
- Do not layer with vitamin C in the same session — alternate nights instead.
- Do not apply to broken, sunburned, or actively irritated skin.
Stop and back off if
- — Stinging past 60 seconds.
- — Visible redness the next morning.
Don't combine with
Same-night use can irritate skin or cancel out the active — alternate nights instead of layering them together.