DMDM Hydantoin
Formaldehyde-releasing preservative. Slowly releases formaldehyde in product. Avoid during pregnancy.
Quick answer
Avoid DMDM hydantoin in pregnancy. It’s a formaldehyde-releasing preservative that slowly emits formaldehyde over the product’s shelf life — exposure source is dermal and via product fumes. Switch to phenoxyethanol-preserved alternatives.
INCI name
DMDM Hydantoin
CAS number
6440-58-0
Also known as
1,3-Dimethylol-5,5-dimethylhydantoin, DMDM
Formula
C7H12N2O4
What is DMDM Hydantoin?
What DMDM hydantoin is
DMDM hydantoin (full name: 1,3-dimethylol-5,5-dimethylhydantoin) is a cosmetic preservative classified as a formaldehyde donor or “formaldehyde-releaser.” The molecule slowly hydrolyzes in water-based formulations, releasing small amounts of free formaldehyde — which provides the antimicrobial action1.
It’s used in shampoos, conditioners, body washes, lotions, and other water-based personal care products at concentrations typically up to 0.6%.
Why it’s avoided in pregnancy
The concern isn’t DMDM hydantoin itself but the formaldehyde it releases. Formaldehyde is an IARC Group 1 human carcinogen, and chronic exposure has been linked to miscarriage in occupational studies2.
Two exposure routes matter for cosmetic formaldehyde donors:
- Dermal absorption. The free formaldehyde released into the product matrix can be absorbed through skin during use.
- Inhalation. Volatile formaldehyde escapes into the air during use, particularly in steamy environments like showers.
Concentrations in any individual product are low, but cumulative exposure from multiple daily-use products (shampoo + conditioner + body wash + lotion) can add up. The American Contact Dermatitis Society named formaldehyde the “Contact Allergen of the Year” in 2015, reflecting its high sensitization rate3.
Other formaldehyde-releasers to recognize
DMDM hydantoin is the most common formaldehyde donor in U.S. cosmetics, but other formaldehyde-releasers to avoid include:
- Imidazolidinyl urea
- Diazolidinyl urea
- Quaternium-15
- 2-Bromo-2-nitropropane-1,3-diol (Bronopol)
- Sodium hydroxymethylglycinate
Most of these have been phased out by EWG-verified and “clean beauty” brands. EU cosmetics regulation requires products containing formaldehyde-releasers above 0.05% to label “contains formaldehyde.”
Safer preservative choices
Phenoxyethanol is the standard pregnancy-safe alternative — FDA, EU SCCS, and Health Canada all accept it up to 1%. Sodium benzoate and potassium sorbate are also low-concern options4.
When to talk to your OB
If you used a product containing DMDM Hydantoin before learning you were pregnant, mention it at your next prenatal visit — but most topical cosmetic exposures are not a cause for panic. For prescription exposures or specific concerns, contact your OB or midwife directly.
Sources
- Cosmetic Ingredient Review Expert Panel. (1988). Final report on the safety assessment of DMDM hydantoin. Journal of the American College of Toxicology. View source →
- International Agency for Research on Cancer. (2012). IARC Monograph 100F: Formaldehyde. IARC. View source →
- Pontén A, Bruze M. (2015). Formaldehyde. American Contact Dermatitis Society — Allergen of the Year. View source →
- European Commission SCCS. (2016). Opinion on phenoxyethanol. SCCS. View source →