Good Active Ingredient NOAEL Data GHS Classified Dermal Penetration

Lactic Acid

INCI: LACTIC ACID

CAS Number
50-21-5
Function
AHA exfoliant (MW 90 Da) with humectant properties. Slightly larger than glycolic acid producing gentler exfoliation. Disrupts corneocyte cohesion and stimulates ceramide biosynthesis (L-isomer). At lower concentrations acts as a skin-identical humectant and Natural Moisturising Factor (NMF) component. Component of Jessner's solution used as a superficial-to-medium peel primer.
Safety Rating
GOOD

Regulatory Status

🇪🇺 EU Status restricted
EU Max Conc. ≤2.5% at pH ≥5.0 for consumer leave-on products
🇺🇸 US Status permitted
US Notes CIR reviewed: safe at ≤10% at pH ≥3.5 (consumer); ≤30% at pH ≥3.0 (professional). FDA references CIR guidance. Photosensitivity advisory applies. Optimal pH range 3.5–5.0 depending on target application. L-isomer clinically preferred for ceramide and barrier benefits.

For full compliance data across 55 jurisdictions, use the Substance Compliance tool.

Safety Data

Margin of Safety (MoS)
adequate
Dermal Absorption
high
Sensitization
low

Calculate MoS for your specific formulation with the MoS Calculator.

Toxicological Studies

3 study endpoints found for Lactic Acid. NOAEL (No Observed Adverse Effect Level) values are used to calculate the Margin of Safety per SCCS methodology.

Endpoint Value Route Species Study Type Source
LOAEL 886 mg/kg bw/day dermal rat dermal REACH
NOAEL 50000 mg/L drinking water other rat oral REACH
NOAEL 50000 mg/L drinking water oral - oral REACH

GHS Hazard Classification

Globally Harmonized System classification per ECHA C&L inventory and ILO/WHO International Chemical Safety Cards.

Short-term Exposure Effects
The substance is corrosive to the eyes. The substance is irritating to the skin and respiratory tract. Corrosive on ingestion.
Routes of Exposure
The substance can be absorbed into the body by inhalation of its aerosol and by ingestion.

Dermal Penetration Profile

Skin absorption and penetration characteristics of Lactic Acid, relevant to systemic exposure and MoS calculations.

Absorption %
12-20%
Penetration Level
epidermis
Penetration Depth
epidermis
Molecular Weight
90.1 Da
Log P
-0.72
Systemic Absorption
minimal
Topical Bioavailability
8-15%
Safety Margin Factor
moderate
Vehicle Dependent
Yes — absorption varies by formulation

Source: CIR 2014

Expert Verdict

Lactic acid is uniquely dual-function: at low concentrations and higher pH it moisturizes via NMF and ceramide activity (L-isomer); at exfoliating concentrations it rivals glycolic acid with slightly gentler kinetics. The EU limit (2.5% pH ≥5.0) effectively caps exfoliating activity. L-lactic acid is strongly preferred over D or racemic forms for barrier-repair formulations. Photosensitivity guidance required.

⚠️
Concern Level: Low

Regulatory Flags

photosensitizing ph-critical l-isomer-preferred humectant-dual-function eu-restricted nmf-component jessners-component eu_children_restricted epa_safer_alternative ifra_fragrance fda_food_additive

Frequently Asked Questions

Is Lactic Acid safe in cosmetics?

Lactic acid is uniquely dual-function: at low concentrations and higher pH it moisturizes via NMF and ceramide activity (L-isomer); at exfoliating concentrations it rivals glycolic acid with slightly gentler kinetics. The EU limit (2.5% pH ≥5.0) effectively caps exfoliating activity. L-lactic acid is strongly preferred over D or racemic forms for barrier-repair formulations. Photosensitivity guidance required. The EU classifies Lactic Acid as "restricted". Safety rating: GOOD. 3 toxicological study endpoint(s) are available in our database.

Is Lactic Acid allowed in the EU?

Lactic Acid EU regulatory status: restricted. Maximum allowed concentration: ≤2.5% at pH ≥5.0 for consumer leave-on products. This is based on EU Regulation 1223/2009 and its amendments.

What does Lactic Acid do in cosmetics?

Lactic Acid functions as: AHA exfoliant (MW 90 Da) with humectant properties. Slightly larger than glycolic acid producing gentler exfoliation. Disrupts corneocyte cohesion and stimulates ceramide biosynthesis (L-isomer). At lower concentrations acts as a skin-identical humectant and Natural Moisturising Factor (NMF) component. Component of Jessner's solution used as a superficial-to-medium peel primer.. It is classified as a Active Ingredient in our database. CAS number: 50-21-5.

What is the Margin of Safety for Lactic Acid?

adequate The Margin of Safety (MoS) is calculated using SCCS methodology. A MoS above 100 is generally considered safe. Use the MoS Calculator tool to calculate MoS for your specific formulation and product category.

What is the NOAEL for Lactic Acid?

The NOAEL (No Observed Adverse Effect Level) for Lactic Acid is 886 mg/kg bw/day based on a dermal study via dermal route in rat. A total of 3 study endpoints are available. Source: REACH.

Compliance Tools

Check Lactic Acid compliance across multiple jurisdictions:

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Ingredient Decoder
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Substance Compliance
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MoS Calculator
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