IgE-mediated urticaria from formaldehyde in a dental root canal compound.

A patient had suffered twice from an acute urticaria after treatment with two different dental root canal compounds (RCC). Skin prick tests with the single components and formaldehyde 1%aq. were positive to formaldehyde 1%aq., but irritant with formaldehydeRCC. Specific IgE to formaldehyde were positive. Patch tests were positive to formaldehydeRCC only. In the literature 28 patients with immediate symptoms to formaldehyde containing RCC have been described.