Multiple application delayed onset contact urticaria: possible relation to certain unusual formalin and textile reactions?

An unusual type of contact urticaria to formalin is described, based on 4 patients and experiments in 14 volunteers. The contact urticaria appeared on healthy skin only following repeated open applications or after a single application on slightly diseased skin. The possible relation of this phenomenon for patients claiming textile intolerance is discussed. Further tests are required to reveal the mechanism of this delayed onset contact urticaria to formalin.