Cited skincare — peer-reviewed evidence, no upsell.

Imidazolidinyl Urea

One of the most widely used preservatives after parabens. Releases trace formaldehyde and cross-reacts in formaldehyde-allergic skin.

What it does

Imidazolidinyl urea is an antimicrobial preservative that became a standard paraben partner — the pairing covers both bacteria and fungi. It releases less formaldehyde than DMDM hydantoin or quaternium-15, but patch-test registries still record consistent positive reactions, and formaldehyde-allergic users typically react across the releaser class. Found in moisturizers, lotions, and makeup as well as rinse-off products. Fine for most skin; skip it if you've flagged a preservative or fragrance sensitivity.

The evidence, graded

strongCommon sensitivity and contact-allergy triggers in skincare include fragrance (the most-cited cosmetic allergen), essential oils, denatured alcohol, and certain preservatives (methylisothiazolinone, formaldehyde-releasers). Patch test new products on the inner forearm for 48–72 hours before face-wide use.Warshaw 2020 · Dermatitis ↗

Graded per the methodology: strong · moderate · emerging · expert consensus. A weak source on a strong claim gets the weaker label.

Also known as

Germall 115

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