Imidazolidinyl Urea
EU-restricted, a common contact allergen, or subject to live debate.
Also written as: Germall 115 · N,N''-Methylenebis[N'-[3-(hydroxymethyl)-2,5-dioxoimidazolidin-4-yl]urea]
What it is
Imidazolidinyl urea is one of the older formaldehyde-releasing preservatives, developed in the 1970s. It releases less formaldehyde than DMDM hydantoin, which is reflected in slightly lower allergy rates, and it is mainly active against bacteria rather than fungi so it is usually paired with a paraben or another antifungal. It remains legal in the EU but has largely fallen out of use in new European formulas.
What it does well
Effective antibacterial protection across a wide pH range
It works well in emulsions where acid-dependent preservatives would fail, which is why it was a workhorse for decades.
Moderate evidence
Worth knowing
Contact allergy, both to the substance and to the formaldehyde it releases
The 2026 meta-analysis put pooled prevalence at 1.20%, the lowest of the common formaldehyde releasers, but still meaningful. People allergic to formaldehyde often react to it.
Matters most toPeople with confirmed formaldehyde or preservative allergy.
Triggers the formaldehyde warning label
If free formaldehyde in the finished product exceeds 10 ppm, the pack must say 'releases formaldehyde'. Seeing that phrase means the product crossed a defined threshold, not that it contains meaningful amounts of free formaldehyde.
Matters most toAnyone scanning labels for formaldehyde exposure.
Where the EU stands
Concentration-restricted
Permitted preservative up to 0.6%. As a formaldehyde releaser, products containing it must carry the warning 'releases formaldehyde' where free formaldehyde exceeds 0.001% (10 ppm).
Regulation (EC) No 1223/2009, Annex V entry 27; labelling rule in the preamble to Annex V as amended by Commission Regulation (EU) 2022/1181 · source ↗
Sources (1)
Every link goes to the original: a journal, a PubMed record or an EU document.
- [1]The Prevalence of Contact Allergy to Formaldehyde and Formaldehyde Releasers: A Systematic Review and Meta-Analysis
Contact Dermatitis · 2026 · doi:10.1111/cod.70172
Pooled contact allergy prevalence for imidazolidinyl urea was 1.20%, the lowest among the formaldehyde releasers assessed, against 2.88% for formaldehyde itself.