Formaldehyde-releasing preservative with a broad spectrum against bacteria and fungi. Works effectively but triggers contact dermatitis.
Topical application
DVery weak or conflicting data.
One of the most active formaldehyde releasers. Patch-test clinics record high sensitization rates, and the EU keeps it under strict control.
Diazolidinyl Urea is a synthetic preservative, a formaldehyde releaser. Releases trace amounts of formaldehyde on hydrolysis in the water phase of a formula, providing a broad antimicrobial spectrum (bacteria, fungi, yeasts). Mechanism. Free formaldehyde binds to microbial proteins and disrupts their function. The released formaldehyde concentration is low (0.003-0.02% depending on formulation) but enough to suppress microflora growth. Where applied. Creams, lotions, shampoos, shower gels, especially in low-cost mass-market lines. In Spain – mass-market Babaria products, budget shampoos, chain-store body care. Manufacturers gradually replace formaldehyde releasers with milder alternatives every year. Evidence base. Preservative efficacy is confirmed by years of practice and standard challenge tests. Stronger than phenoxyethanol and caprylhydroxamic acid in high-microbial-risk systems. Safety and controversies. CIR in 2014 confirmed diazolidinyl urea safety up to 0.5% in cosmetics. The EU allows Diazolidinyl Urea in leave-on and rinse-off up to 0.5% (Regulation 1223/2009, Annex V). At the same time, diazolidinyl urea is one of the top preservatives for contact allergy frequency: per NACDG (North American Contact Dermatitis Group) data, sensitization in 3-5% of patients suspected of preservative allergy. Pregnancy and lactation – with caution. No direct ban, but in sensitive skin and contact dermatitis tendency – avoid. Milder-profile alternatives are available. Best suited to: healthy skin without contact allergy tendency. Not for atopy, eczema, or formaldehyde allergy history. For sensitive skin and 'clean' formulas check the label for 'Diazolidinyl Urea', 'Imidazolidinyl Urea', 'DMDM Hydantoin', 'Quaternium-15' – all these preservatives are in the risk group. This is a formaldehyde-releasing preservative: in the water phase it slowly gives off small amounts of free formaldehyde. If you are allergic to formaldehyde or have very sensitive skin, choose a product without it – at permitted levels the risk for everyone else is low. When several such preservatives are combined, their formaldehyde adds up, and in the EU a total above 0.001% requires a "releases formaldehyde" label. It often appears next to parabens on the label – that is not a reaction between them but a ready-made preservative blend (e.g. Germaben): the urea releases formaldehyde, parabens have nothing to do with it.
Irritation potential
MediumAllergen risk
HighPregnancy
CautionReleases formaldehyde
This is a formaldehyde-releasing preservative: it slowly gives off small amounts of formaldehyde in the water phase. If you are allergic to formaldehyde or have very sensitive skin, choose a product without it. At permitted levels the risk for everyone else is low. When several such preservatives are combined, their formaldehyde adds up – that matters more than any single one.
Use with caution
The Evigrade extension adds an evidence panel to iHerb, Sephora, Druni and 12 more stores. This ingredient and every other one in the product show evidence-tier, allergen risk and pregnancy/lactation flags at a glance.
Diazolidinyl Urea should be used with caution during pregnancy. Consulting a dermatologist or OB-GYN is advisable.
Use with caution in: sensitive.
Diazolidinyl Urea has moderate irritation potential. Sensitive skin may show a transient reaction that usually settles with adaptation.
Diazolidinyl Urea has high allergen potential. Perform a patch test on the inner forearm 24 hours before facial application.
Formaldehyde-releasing preservative with a broad spectrum against bacteria and fungi.
The INCI name is Diazolidinyl Urea.
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