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CarCareTruth

DMDM Hydantoin

  • Preservatives
  • CAS 6440-58-0
  • IUPAC: 1,3-bis(hydroxymethyl)-5,5-dimethylimidazolidine-2,4-dione

DMDM Hydantoin (CAS 6440-58-0) appears in 23 of the 2,122 car-care products CarCareTruth tracks (as of August 2026). It is readily biodegradable.

DMDM hydantoin is a formaldehyde-releasing preservative; at occupational concentrate levels it is classified H317 (may cause an allergic skin reaction). DMDM hydantoin itself is not on California's Prop 65 list, though the formaldehyde it can release is listed separately. At the trace use concentrations typical in car-care products (≤0.003%), released formaldehyde is far below Prop 65 thresholds and the respiratory-sensitizer classification (H334) does not apply to the finished product.

DMDM Hydantoin is a formaldehyde-releasing preservative (biocide) used at trace concentrations (typically ≤ 0.003%) to prevent microbial growth in water-based formulas. It releases small amounts of formaldehyde as a byproduct of its antimicrobial mechanism. DMDM Hydantoin itself is not on the Prop 65 list (CAS 6440-58-0); formaldehyde (CAS 50-00-0) is listed separately but is only relevant at the concentrations where it is present — at ≤ 0.002% DMDM Hydantoin the released formaldehyde is far below any Prop 65 threshold. Not an asthmagen at these use concentrations; H334 respiratory sensitizer classification does not apply. At occupational concentrate levels (>0.1%) it can cause allergic skin reactions (H317 skin sensitizer) in sensitive individuals.

Health & environment profile

VOC
no
Prop 65 listed
no
Asthmagen
no
EPA Safer Choice
no
Aquatic toxicity
no
Biodegradable
yes
Bioaccumulative
no
Persistent
no
Ozone depleting
no
Microplastic
no
PFAS
no
Env. score
4/5
Purpose: Formaldehyde-releasing preservative; antimicrobial at trace concentrations

Common questions about DMDM Hydantoin

What is DMDM Hydantoin used for in car care?
Formaldehyde-releasing preservative; antimicrobial at trace concentrations
Is DMDM Hydantoin a VOC?
No. DMDM Hydantoin is not classified as a volatile organic compound (VOC).
Is DMDM Hydantoin on California's Proposition 65 list?
No. DMDM Hydantoin is not on California's Proposition 65 list.
Is DMDM Hydantoin biodegradable?
Yes. DMDM Hydantoin has a confirmed biodegradable profile.

23 products contain this

Related

Health and environment notes translate the manufacturer Safety Data Sheet, the GHS classification, and authoritative regulatory listings (California Prop 65, EPA). Not medical advice. They describe the ingredient itself; whether a hazard applies to a finished product depends on its concentration and how it's used.