Characterization and chemistry of imidazolidinyl urea and diazolidinyl urea

For several decades, the cosmetic preservatives imidazolidinyl urea (IU) and diazolidinyl urea (DU) have not only been poorly characterized but have also had misleading chemical structures assigned to them. The most common trade names of IU and DU are Germall 115 and Germall II, respectively. This publication gives an insight into what these 2 well‐known contact allergens consist of and their degradation patterns. Approximately, 30–40% of both products can be characterized by mixtures of allantoin (synthetic starting material), (4‐hydroxymethyl‐2,5‐dioxo‐imidazolidin‐4‐yl)‐urea (compound HU) and presumably 1‐(3,4‐bis‐hydroxymethyl‐2,5‐dioxo‐imidazolidin‐4‐yl)‐1,3‐bis‐hydroxymethyl‐urea (compound BHU). A full chemical characterization of compound HU is shown. The remaining part of both IU and DU are believed to be polymers of allantoin‐formaldehyde condensation products. The analytical methods used to characterize IU and DU are capillary electrophoresis and nuclear magnetic resonance and mass spectroscopy studies.