Chapter 6: Preservatives
DMDM hydantoin
- Officially classed skin allergen
- Made from a hazardous chemical
- Contaminant risk
The worst fact: it's built to release formaldehyde, a known cause of cancer. It's first on Washington State's list of formaldehyde releasers banned in cosmetics from 1 January 2027. In Europe, cosmetics must now say "releases formaldehyde" once it releases more than 0.001% (10 parts per million).
Why brands use it: it's an effective, long-used preservative.
Take care if: you're allergic to formaldehyde.
Comes from: dimethylhydantoin reacted with formaldehyde. Australia classes formaldehyde as "May cause cancer". That doesn't mean extra is added, but it's not a great starting point for something you clean with.
Myth check: "it's proven to cause hair loss": lawsuits claimed it, but the main US case against TRESemmé was dismissed in 2022.
Contaminants: free formaldehyde. It's there by design, because that's how it works.
Fair to say: US cosmetic safety reviewers found it safe as used, but people allergic to formaldehyde should avoid it.
Correct as of November 2026. What the badges mean
Sources
- Safe Work Australia. Hazardous Chemical Information System (HCIS): classifications for each chemical and for benzene, ethylene oxide, toluene, phenol and benzyl chloride. hcis.safeworkaustralia.gov.au
- US Cosmetic Ingredient Review. Final report on DMDM hydantoin (1988).
The full source list is at the end of Chapter 6.