Background: Exercise-induced anaphylaxis (EIA) is a unique physical allergy that is triggered by exertion, the clinical spectrum and modifying factors of which have been previously studied. At the time of initial description, it was postulated that other factors contributed to this disorder.
Objective: We sought to determine the clinical course and potential modifying factors in EIA.
Methods: In 1993, we conducted a cross-sectional analysis of 671 individuals with exercise-associated symptoms for more than a decade using a validated 75-item questionnaire. Subjects met criteria for EIA if they had anaphylactic symptoms, including hypotension or upper airway obstruction, urticaria, or angioedema with physical exertion but without a passive increase in core body temperature.
Results: Of 365 (54%) questionnaire respondents, 279 (87%) met criteria for EIA (199 females and 80 males). At the time of study entry, subjects with EIA (mean age, 37.5 years; range, 13 to 77 years) had an average of 10.6 years of symptoms, which were most frequently triggered by aerobic activities such as jogging or brisk walking (78% and 42%, respectively). On average, subjects reported that the frequency of attacks had decreased (47% of subjects) or stabilized (46% of subjects) since onset. One hundred (41%) subjects reported being completely free of attacks in the past year. Subjects reduced their attacks by avoiding exercise during extremely hot or cold weather (44%), avoiding ingestion of certain foods before exercise (37%), and restricting exercise during their allergy season (36%) or humid weather (33%). The most common pharmacologic agents used to manage symptoms were H1 antagonists (56%) and/or epinephrine (31%). However, 28% used no treatment at all.
Conclusion: EIA is an episodic condition in which the frequency of attacks tends to stabilize or decrease over time. Improvement appears to result from individual modification of exercise and avoidance of known environmental and ingestible precipitants.