Characterization of the decomposition of compounds derived from imidazolidinyl urea in cosmetics and patch test materials

Background: Imidazolidinyl urea releases formaldehyde through decomposition. However, there have been few reports on the chemistry of imidazolidinyl urea in cosmetics.

Objectives: The aim of this study was to characterize imidazolidinyl urea-derived compounds in cosmetics and to determine which compounds are responsible for the cross-reactivity with diazolidinyl urea.

Methods: We analysed imidazolidinyl urea dissolved in aqueous solutions, imidazolidinyl urea patch test Materials and imidazolidinyl urea-preserved cosmetics by high-performance liquid chromatography/photodiode array detection and liquid chromatography/mass spectrometry. The results were compared with those obtained with a diazolidinyl urea aqueous solution.

Results: In the analysed cosmetic samples and patch test Materials, imidazolidinyl urea was primarily composed of allantoin, (4-hydroxymethyl-2,5-dioxo-imidazolidine-4-yl)-urea (HU), (3,4-bis-hydroxymethyl-2,5-dioxo-imidazolidine-4-yl)-urea (3,4-BHU), and (3-hydroxymethyl-2,5-dioxo-imidazolidine-4-yl)-urea.

Conclusions: Two of the imidazolidinyl urea-derived major decomposition compounds - HU and 3,4-BHU - are common in the diazolidinyl urea-decomposed compound present in cosmetics. These compounds are possible causative agents of the cross-reactivity between diazolidinyl urea and imidazolidinyl urea.