The spectrum of contact urticaria. Wheals, erythema, and pruritus

A large variety of topical substances can provoke wheals of human skin within 30 minutes. The usual term for this phenomenon, "contact urticaria," is too constricting and can lead to faulty diagnosis. Sometimes, the clinical expression is limited to erythema; less often, its sole manifestation is pruritus. The author proposes that contact urticaria is a spectrum ranging from urticaria through erythema to pruritus alone. This spectrum was demonstrated experimentally with three familiar urticariogens: cinnamic aldehyde and sorbic and benzoic acids. The nature of the immediate reaction depended on the concentration: wheals were induced with the highest tested concentration, erythema with a five-fold dilution, and pruritus alone with a 25-fold dilution.