Preservative considered weaker than its “cousin” diazolidinyl urea because it is active against bacteria but does not have the antifungal action of diazolidinyl urea. Most often used with parabens because they work well together. Imidazolidinyl urea is considered a formaldehyde-releasing preservative. Although that sounds scary, the amount of formaldehyde released is well below the limits for safe exposure. Still, some regulatory experts caution against using products with imidazolidinyl urea on infants. 
- Rastogi S. Analytical control of preservative labelling on skin creams. Contact Dermatitis. 2000;43(6):339-43.