Diazolidinyl urea is primarily an antibacterial preservative, with activity against moulds but fairly weak anti-yeast activity. It has been widely used in many markets since its introduction in the 1980s. It is classified as a formaldehyde donor.

Diazolidinyl urea is highly water-soluble and should be added to the product at temperatures below 40°C to avoid decomposition. It retains its activity over a broad pH range, from pH 3 to 9. Typical use concentrations are 0.1–0.3%. Diazolidinyl urea is permitted in many territories, with restrictions.

Source: Cosmetic Formulation Principles and Practice - Heather A.E. Benson, Michael S. Roberts, Vânia Rodrigues Leite-Silva, Kenneth A. Walters

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