Considered a weaker preservative than its "cousin" diazolidinyl urea because it is active against bacteria but does not maintain the anti-fungal action of diazolidinyl urea. Most often used with parabens, as they work well together. Imidazolidinyl urea is considered a formaldehyde-releasing preservative (Source: Contact Dermatitis
, December 2000, pages 339–343). Although that sounds scary, the amount of formaldehyde released is considered well below the limits for safe exposure. Still, some regulatory experts caution against using products with imidazolidinyl urea on infants.