Imidazolidinyl Urea Mauvais Conservateur No known benefits Imidazolidinyl Urea description Preservative considered weaker than its “cousin” 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. Related ingredients: Diazolidinyl Urea