Environmentally induced cholinergic urticaria and anaphylaxis.

Although urticaria is generally an uncomfortable condition, it is usually considered to be relatively benign. Recent evidence indicates that numerous environmental stimuli can initiate cholinergic urticaria, and severe systemic manifestations may be associated with the onset of the urticaria. Exercise-induced anaphylaxis is a specific life-threatening reaction that has been documented to occur very unpredictably in susceptible individuals with cholinergic urticaria. The occurrence of severe hypotension, syncope, or laryngeal edema poses specific limitations to optimum performance should it occur in individuals employed in critical occupations. Although treatment with appropriate medications is generally effective in control of symptoms, these medications frequently have side effects not tolerable in high-risk situations. Four cases of U.S. Air Force aircrewmen referred to the USAF School of Aerospace Medicine for aeromedical evaluation illustrate the spectrum of problems that can be associated with cholinergic urticaria. Exercise history should always be carefully evaluated in all individuals who present with urticaria.