AIRWAY RESPONSIVENESS TO ALLERGEN IS INCREASED 24 HOURS AFTER EXERCISE CHALLENGE

Although exercise is one of the most ubiquitous triggers of acute bout s of asthma, the changes in airway responsiveness before and after exe rcise are not well defined. Specifically, the effect of the changes in airway responsiveness induced by exercise has not been studied on sub sequent allergen exposure. To test whether the reactivity to allergen is altered by preceding exercise and to define possible factors determ ining it, we subjected 24 children with atopic asthma to the relevant allergen challenge on two occasions: one as a control without a preced ing procedure and the other 24 hours after exercise challenge. Mean po stallergen maximal percent falls in forced expiratory volume in 1 seco nd from baseline (Delta FEV(1)) of the whole group were higher after t he exercise challenge compared with those of control in both early (<1 hour) and late (3 to 10 hours) phases. The changes of postallergen ma ximal Delta FEV(1) between the control and post-exercise allergen chal lenges were not related to the early bronchial response to the precedi ng exercise challenge. Late asthmatic responses to exercise developed in six children, and the changes in both early and late phases were si gnificantly higher in these children, compared with those without late asthmatic responses. Furthermore, the changes were well correlated wi th the magnitude of the late-phase response to preceding exercise in t he group as a whole. It is concluded that an increased airway responsi veness to allergen occurs 24 hours after exercise in some patients wit h asthma. As the changes are related to a late bronchial response to e xercise, late asthmatic response to exercise when it occurs, may be as sociated with increased asthmatic symptoms for as long as 24 hours aft er exercise.