Mediator release in local heat urticaria.

We described the sixteenth reported case of local heat urticaria, in a 59-yr-old woman with erythema and angioedema upon contact with hot water or outdoor heat exposure. Immersing her hand in 39 degrees to 40 degrees C heated water resulted in an erythematous, angioedematous response sharply demarcated by the line of immersion and was associated with immediate increases in histamine concentration (18 to 135 ng/ml) and high molecular weight neutrophil chemotactic activity (two to five times prechallenge levels) in venous blood draining the challenge site. We suggest that the local heat urticarial response in this woman was a form of physical urticaria associated with release of mast cell-derived mediators, akin to cold and cholinergic urticaria.