Lactic Acid
AHA with dual action: acid exfoliation and moisturization via hygroscopicity. Gentler than glycolic acid.
Evidence by route
Topical application
Clinical studies demonstrate efficacy for xerosis, keratosis, and hyperpigmentation. Less potent than glycolic acid for exfoliation but better tolerated. Use in melasma is supported by randomized trials.
- Oresajo C et al. J Cosmet Laser Ther. 2010;12(3):157-62. PMID 20429687
How to read tiers A–F
- BLimited evidence. One RCT or several controlled studies with limitations
Tolerability and safety
- Working concentrations
- 2–12%
- Irritation potential
- Medium
- Allergen risk
- Low
- Pregnancy
- Caution
- Suitable for
- Normal, Dry, Combination
- Use with caution
- Sensitive
About this ingredient
Lactic Acid is a two-carbon alpha-hydroxy acid (AHA), a natural metabolite of lactic fermentation. Found in sour milk (hence the name), kefir, and in human sweat. Produced synthetically or by Lactobacillus fermentation. Mechanism. At low pH (3.5-4.0) it loosens desmosomal bonds between corneocytes in the stratum corneum – cells shed more easily. This reduces hyperkeratosis, evens out texture, and lightens pigmentation. Additionally lactic acid is a component of the natural moisturizing factor (NMF), binds water, and hydrates the stratum corneum. This dual effect distinguishes it from glycolic acid (which only exfoliates). Where applied. Exfoliants, toners, creams, masks (5-10% in cosmetics, up to 20-30% in peel formulas). Professional dermatological peels – 30-70%. In Spain – Sesderma Acglicolic, The Ordinary Lactic Acid 5%/10%, Mesoestetic Glycolic Solution, Avène Cleanance ACne Mask. Evidence base. Smith 1996, Stiller 1996, Tasic-Kostov 2010 – RCTs with 5-12% lactic acid in photoaged patients: improved texture, reduced fine wrinkles, lightened pigmentation over 12 weeks. Less irritating than glycolic acid at comparable efficacy. Well suited for dry and sensitive skin. Safety. CIR rated lactic acid safe at cosmetic concentrations up to 10% at pH ≥3.5 (1998, re-evaluated 2017). EU SCCS confirmed safety. Irritation possible at high concentrations and low pH – especially in the first weeks of use. Increases photosensitivity – SPF 30+ during the day is mandatory. Pregnancy and lactation – safe topically at cosmetic concentrations. Suitable for dry, sensitive, mature skin, for pigmentation, post-inflammatory hyperpigmentation, ichthyosis. With active rosacea and herpes – use with caution.
Frequently asked questions
Is Lactic Acid safe during pregnancy?
Lactic Acid should be used with caution during pregnancy. Consulting a dermatologist or OB-GYN is advisable.
What skin types is Lactic Acid for?
Lactic Acid suits: normal, dry, combination. Use with caution in: sensitive.
Can Lactic Acid irritate the skin?
Lactic Acid has moderate irritation potential. Sensitive skin may show a transient reaction that usually settles with adaptation.
What is Lactic Acid and what does it do in cosmetics?
AHA with dual action: acid exfoliation and moisturization via hygroscopicity.
What's the INCI name for Lactic Acid?
The INCI name is Lactic Acid. It may also appear as: 2-Hydroxypropanoic Acid.
What concentration of Lactic Acid is effective?
2–12%
See Lactic Acid in a product composition right on the store page
The Evigrade extension adds an evidence panel to iHerb, Sephora, Druni and 12 more stores. This ingredient and every other one in the product show evidence-tier, allergen risk and pregnancy/lactation flags at a glance.
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