Body & Beauty / Compounds / DMDM hydantoin

DMDM hydantoin on your skin: a safety profile

Moderate risk

Dermal contact is the primary exposure route for DMDM hydantoin in cosmetic use. Leave-on products (moisturizers, conditioners) contribute far more to dermal formaldehyde release exposure than rinse-off products (shampoos, body wash) because exposure time is much longer. Patch testing databases (NACDG, IVDK) consistently show DMDM hydantoin positivity rates of 1–3% in patients with suspected contact dermatitis, making it one of the more common cosmetic preservative allergens in clinical testing. In sensitized individuals, even trace amounts in cosmetic products can trigger allergic contact dermatitis — a delayed-type (Type IV) hypersensitivity reaction presenting as eczema, erythema, and pruritus at contact sites (scalp, face, hands). DMDM hydantoin can cross-react with other formaldehyde releasers (imidazolidinyl urea, diazolidinyl urea, quaternium-15) and with formaldehyde itself. Occupational exposure among hairdressers, cosmetologists, and personal care product manufacturing workers represents a higher cumulative exposure scenario. The EU SCCS has evaluated DMDM hydantoin and concluded that at maximum permitted concentrations in cosmetics, it is safe for non-sensitized consumers but that sensitized individuals should avoid products containing it.

What is dmdm hydantoin?

The IUPAC name is 1,3-bis(hydroxymethyl)-5,5-dimethylimidazolidine-2,4-dione.

Also known as: 1,3-bis(hydroxymethyl)-5,5-dimethylimidazolidine-2,4-dione, Dmdmh, Glydant, 1,3-Bis(hydroxymethyl)-5,5-dimethylhydantoin.

IUPAC name: 1,3-bis(hydroxymethyl)-5,5-dimethylimidazolidine-2,4-dione
CAS number: 6440-58-0
Molecular formula: C7H12N2O4
Molecular weight: 188.18 g/mol
SMILES: CC1(C(=O)N(C(=O)N1CO)CO)C
PubChem CID: 22947

Risk for people

Moderate risk

Regulatory consensus

12 regulatory and scientific bodies have classified DMDM hydantoin. The classifications differ — that's the data.

Agency	Year	Classification
US EPA	2000	not classifiable as to human carcinogenicity (Group D)
EFSA	2010	not evaluated for carcinogenicity; contact sensitizer and formaldehyde releaser regulated under EU Cosmetics Regulation (EC) No 1223/2009 Annex V (preservatives); maximum authorized concentration 1% (as formaldehyde equivalent); mandatory labeling above 0.05% free formaldehyde
EPA CTX / Genetox	—	Genotoxicity: positive (Ames: positive, 4 positive / 4 negative reports)
EPA CTX / Genetox	—	Genotoxicity: positive (Ames: positive, 4 positive / 4 negative reports)
EPA CTX / Skin-Eye	—	Skin Sensitization: Sh (score: high)
EPA CTX / Skin-Eye	—	Skin Irritation: SkinIrr2 (score: high)
EPA CTX / Skin-Eye	—	Skin Sensitization: SkinSens1 (score: high)
EPA CTX / Skin-Eye	—	Skin Irritation: Category 6.3B (Category 3) (score: moderate)
EPA CTX / Skin-Eye	—	Skin Sensitization: Category 6.5B (Category 1) (score: moderate)
EPA CTX / Skin-Eye	—	skin irritation: in vivo: Moderate or Mild Irritation (score: moderate)
EPA CTX / Skin-Eye	—	eye irritation: in vivo: Moderate or Mild Irritation (score: moderate)
EPA CTX / Skin-Eye	—	skin sensitisation: in vivo (non-LLNA): Not likely to be sensitizing (score: low)

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 dmdm hydantoin

Industrial Facilities — Manufacturing plants, Chemical storage areas, Waste treatment sites
Occupational Environments — Factories, Warehouses, Transportation vehicles
Personal Care — shampoo, conditioner, lotion, cosmetics, sunscreen

Safer alternatives

Lower-risk approaches that achieve a similar outcome to DMDM hydantoin:

Physical/mechanical pest control (IPM)
Trade-offs: More labor-intensive. May not be sufficient for severe infestations.

Relative cost: Variable; lower long-term
Phenoxyethanol
Relative cost: 1.2-2×
Sodium benzoate + potassium sorbate
Relative cost: 1.2-2×
Caprylyl glycol
Relative cost: 1.2-2×

Frequently asked questions

Is dmdm hydantoin safe for you?

What products contain dmdm hydantoin?

DMDM hydantoin appears in: Manufacturing plants (Industrial facilities); Chemical storage areas (Industrial facilities); Factories (Occupational environments); Warehouses (Occupational environments); shampoo (Personal care).

Why do regulators disagree about dmdm hydantoin?

DMDM hydantoin has been classified by 12 agencies including US EPA, EFSA, EPA CTX / Genetox, EPA CTX / Genetox, EPA CTX / Skin-Eye, with differing conclusions. 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. See the regulatory consensus table on this page for the full picture.

See DMDM hydantoin in the body app

Look up products containing dmdm hydantoin, compare to alternatives, and explore the full data record.

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Sources (2)

US EPA DMDM Hydantoin: Group D Not Classifiable Carcinogen; Formaldehyde-Releasing Preservative; Contact Sensitizer; Cumulative Formaldehyde Exposure; FDA 2024 Proposed Cosmetic Restriction; Patch Test Positivity 1–4% (2000) — regulatory
EFSA/SCCS DMDM Hydantoin: EU Cosmetics Regulation Annex V Permitted Preservative; Maximum 1% (as formaldehyde equivalent); Mandatory Labeling >0.05% Free Formaldehyde; Contact Sensitization Critical Endpoint; REACH Restriction Review (2010) — 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 →