Body & Beauty / Compounds / Lactic acid

Lactic acid on your skin: a safety profile

Low risk

(People-specific data is limited; this page draws from human adult context.) Lactic acid (2-hydroxypropanoic acid; CH₃CHOHCOOH; E270) is an alpha-hydroxy acid (AHA) produced by anaerobic fermentation and glycolysis — it is both a natural metabolite (produced at ~1200 mg/kg/hr during intense exercise via anaerobic glycolysis in skeletal muscle) and a widely used food additive, cosmetic ingredient, and pharmaceutical excipient. Biological role: lactic acid is central to energy metabolism — during intense exercise, pyruvate is converted to lactate by lactate dehydrogenase (LDH) when oxygen delivery is insufficient for aerobic oxidation; lactate is then oxidized in the liver and heart (Cori cycle), or reconverted to pyruvate in oxidative muscle fibers as exercise intensity decreases. Food applications: lactic acid (produced by fermentation of carbohydrates by Lactobacillus spp.) is the acidulant in yogurt, sour cream, buttermilk, cheese, sourdough bread, fermented meats (salami, pepperoni), and pickled vegetables; it is also added directly as E270 to regulate pH and extend shelf life. FDA GRAS status: lactic acid is GRAS as a food acidulant, pH adjuster, and flavoring agent; ADI 'not specified' (JECFA). Cosmetic/personal care: lactic acid 5–12% is used in chemical exfoliant products (AHA peels) to improve skin texture, reduce fine lines, and treat hyperpigmentation by dissolving corneocyte adhesion in the stratum corneum; prescription concentrations up to 30% are used by dermatologists. No carcinogen classification. Acute oral toxicity: very low — oral LD50 rat ~3700 mg/kg.

What is lactic acid?

The IUPAC name is 2-hydroxypropanoic acid.

Also known as: 2-hydroxypropanoic acid, DL-Lactic acid, 2-hydroxypropionic acid, Milk acid.

IUPAC name
2-hydroxypropanoic acid
CAS number
50-21-5
Molecular formula
C3H6O3
Molecular weight
90.08 g/mol
SMILES
CC(C(=O)O)O
PubChem CID
612

Risk for people

Low risk

Lactic acid (2-hydroxypropanoic acid; CH₃CHOHCOOH; E270) is an alpha-hydroxy acid (AHA) produced by anaerobic fermentation and glycolysis — it is both a natural metabolite (produced at ~1200 mg/kg/hr during intense exercise via anaerobic glycolysis in skeletal muscle) and a widely used food additive, cosmetic ingredient, and pharmaceutical excipient. Biological role: lactic acid is central to energy metabolism — during intense exercise, pyruvate is converted to lactate by lactate dehydrogenase (LDH) when oxygen delivery is insufficient for aerobic oxidation; lactate is then oxidized in the liver and heart (Cori cycle), or reconverted to pyruvate in oxidative muscle fibers as exercise intensity decreases. Food applications: lactic acid (produced by fermentation of carbohydrates by Lactobacillus spp.) is the acidulant in yogurt, sour cream, buttermilk, cheese, sourdough bread, fermented meats (salami, pepperoni), and pickled vegetables; it is also added directly as E270 to regulate pH and extend shelf life. FDA GRAS status: lactic acid is GRAS as a food acidulant, pH adjuster, and flavoring agent; ADI 'not specified' (JECFA). Cosmetic/personal care: lactic acid 5–12% is used in chemical exfoliant products (AHA peels) to improve skin texture, reduce fine lines, and treat hyperpigmentation by dissolving corneocyte adhesion in the stratum corneum; prescription concentrations up to 30% are used by dermatologists. No carcinogen classification. Acute oral toxicity: very low — oral LD50 rat ~3700 mg/kg.

Regulatory consensus

2 regulatory and scientific bodies have classified Lactic acid. The classifications differ — that's the data.

AgencyYearClassificationNotes
EPA CTX / Genetox—Genotoxicity: positive (Ames: positive, 3 positive / 10 negative reports)
EPA CTX / Genetox—Genotoxicity: positive (Ames: positive, 3 positive / 10 negative reports)

Regulators apply different standards of evidence — animal-data weighting, exposure-pattern assumptions, epidemiological power thresholds — which is why two scientific bodies can review the same data and reach different conclusions. The disagreement is the data.

Where you encounter lactic acid

  • Industrial Facilities — Manufacturing plants, Chemical storage areas, Waste treatment sites
  • Occupational Environments — Factories, Warehouses, Transportation vehicles
  • Food — processed food, beverages, candy, baked goods
  • Fragrance — perfume, cologne, scented personal care products, household fragrance products, candles
    Identified in Fragrance Ingredient Safety Priority Research database (2,325 ingredients)

Safer alternatives

Lower-risk approaches that achieve a similar outcome to Lactic acid:

  • Physical/mechanical pest control (IPM)
    Trade-offs: More labor-intensive. May not be sufficient for severe infestations.
    Relative cost: 1.2-2×

Frequently asked questions

What products contain lactic acid?

Lactic acid appears in: Manufacturing plants (Industrial facilities); Chemical storage areas (Industrial facilities); Factories (Occupational environments); Warehouses (Occupational environments); processed food (Food).

See Lactic acid in the body app

Look up products containing lactic acid, compare to alternatives, and explore the full data record.

Open in body View raw API data

Sources (2)
  1. FDA GRAS: Lactic Acid (21 CFR 184.1061) — E270; fermented food acidulant; Lactated Ringer's solution; AHA cosmetics; Cori cycle; oral LD50 3700 mg/kg; ADI not specified (2021) (2021) — regulatory
  2. EFSA ANS Panel: Lactic Acid (E 270) — ADI not specified; dietary exposure; fermented foods; pediatric IV use; safety conclusion; endogenous metabolite status (2013) (2013) — regulatory

Reference data, not professional advice. Aggregates publicly available regulatory and scientific data; not a substitute for veterinary, medical, legal, or regulatory advice. Why we built ALETHEIA →