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preservative

DMDM Hydantoin

Watch if sensitive·Strong evidence

A preservative that works by slowly releasing small amounts of formaldehyde to control microbial growth. This makes it an effective preservative, but people with a known formaldehyde or fragrance-type sensitivity may develop irritation or an allergic reaction, especially with prolonged use of leave-on products.

Worth knowing

  • Known contact sensitizer for some
  • Can irritate, especially left on
  • Restricted in the EU

EU rules cap free formaldehyde release and require a "contains formaldehyde" warning on the label once free formaldehyde exceeds 0.05%.

Gentler alternatives

Questions

Does DMDM hydantoin release formaldehyde in cosmetics?
Yes, DMDM hydantoin works by slowly releasing small amounts of formaldehyde to control microbial growth. The EU limits free formaldehyde release in cosmetics and requires a label warning once levels exceed 0.05%. People with a known formaldehyde sensitivity or reactive skin should patch test or avoid products containing this preservative.
Is DMDM hydantoin safe despite releasing formaldehyde?
DMDM hydantoin is an effective preservative at regulated concentrations with restrictions on free formaldehyde release. The primary safety concern is for people with existing sensitivities to formaldehyde or fragrances. For most people at typical use levels in rinse-off products, the risk profile is low; leave-on products carry higher exposure potential.

Products with DMDM Hydantoin

In our guides

References

Cosmetic information for general education, not medical advice. A verdict is a reading of the published evidence, never a guarantee for your skin: any ingredient can irritate someone, so patch test new products and see a professional if you react. Concern is graded on cited evidence, never on hazard-score lists. See how we score.