At a glance
- CAS number
- 50-21-5
- INCI name
- Lactic Acid
- Function
- ph_adjuster, humectant, active, exfoliant
- Typical use level
- 0.5%–12%
- Solubility
- water
- Stable pH
- 2.5–4.5
CAS number and synonyms are sourced from PubChem. Function, usage levels, pH and compatibility are AI-assisted formulation guidance — verify against your supplier's technical data sheet and applicable regulations before use.
Also known as
lactic acid 2-hydroxypropanoic acid DL-Lactic acid 2-hydroxypropionic acid Milk acid Tonsillosan Racemic lactic acid Ordinary lactic acid Acidum lacticum Ethylidenelactic acid Lactovagan Milchsaeure
Compatibility
Works well with:
Glycerin Hyaluronic Acid Niacinamide Sodium Lactate Allantoin Panthenol Aloe Vera Sodium PCA Urea
Use caution with:
Retinol Benzoyl Peroxide Vitamin C (L-Ascorbic Acid) Salicylic Acid Strong Bases
Lactic acid can lower pH significantly, potentially destabilizing other pH-sensitive actives like retinol or causing irritation when combined with other exfoliating acids. Combining with benzoyl peroxide or multiple AHAs increases irritation risk and should be approached with caution. Strong bases will neutralize lactic acid, reducing its efficacy as both a pH adjuster and exfoliant.
Formulation notes
In the EU, leave-on products containing AHAs above 10% (as acid) require a pH ≥ 3.5 and a specific warning label; rinse-off products have separate thresholds. At concentrations above 4-5% with low pH, it functions as a chemical exfoliant (AHA); at lower levels it acts primarily as a humectant and pH adjuster. Sun sensitivity warning may be required at exfoliant-level concentrations. CAS: 50-21-5.
Frequently asked questions
What is Lactic Acid?
Lactic Acid is a ph_adjuster, humectant, active, exfoliant used in cosmetic and personal-care formulation. Typical use level is 0.5%–12%. It is water-soluble. Stable in the pH 2.5–4.5 range.
What is Lactic Acid used for?
Lactic Acid is used as ph_adjuster, humectant, active, exfoliant in cosmetic and personal-care formulations.
What is the typical use level of Lactic Acid?
Lactic Acid is typically used at 0.5%–12% in the finished formulation. Always confirm against your supplier's technical data sheet.
What is the CAS number of Lactic Acid?
The CAS registry number for Lactic Acid is 50-21-5. Its INCI name is Lactic Acid.
At what pH is Lactic Acid stable?
Lactic Acid is generally stable in the pH 2.5–4.5 range.
What ingredients are compatible with Lactic Acid?
Lactic Acid works well with Glycerin, Hyaluronic Acid, Niacinamide, Sodium Lactate, Allantoin, Panthenol, Aloe Vera, Sodium PCA, Urea. Use caution when combining it with Retinol, Benzoyl Peroxide, Vitamin C (L-Ascorbic Acid), Salicylic Acid, Strong Bases.
Related ingredients
- Glycolic AcidActive
- Citric AcidPh Adjuster
- Ascorbic AcidAntioxidant
- Capryloyl Salicylic AcidExfoliant
- GluconolactoneExfoliant
- Mandelic AcidExfoliant