Imidazolidinyl Urea

Imidazolidinyl urea is a formaldehyde-releasing preservative typically used around ~0.1–0.6% in leave-on and rinse-off products. It is a well-documented trigger for allergic contact dermatitis (and can sting/irritate compromised skin), with sensitization risk heightened in eczema-prone and barrier-impaired patients. Given its recognized allergen potential and the real-world likelihood of cumulative exposure across multiple products, it warrants a notable irritancy score for sensitive-skin safety. Safety Notes: In consumer cosmetics, imidazolidinyl urea is typically used as a formaldehyde-releasing preservative around 0.1–0.3%, with very low-end uses (~0.05%) occurring in multi-preservative systems where it is only a minor contributor (common in both leave-on lotions and rinse-off cleansers). Higher-strength OTC products (especially economical creams/lotions and some haircare where stronger preservation is needed) are observed up to about 0.5–0.6%, which aligns with common supplier/industry maximum-use guidance for cosmetic preservation rather than prescription/professional-only levels.