THE OCCURRENCE OF LATE ASTHMATIC RESPONSE TO EXERCISE AFTER ALLERGEN CHALLENGE

Background: The determinants of late asthmatic responses to exercise r emain unknown. It has been reported that they may develop in some adul t subjects with asthma following a late asthmatic response to allergen . Objective: We intended to corroborate this finding in children with asthma and to investigate which aspect of airway responses to allergen is associated with late asthmatic responses to exercise. Methods: We studied 17 children with allergic asthma, who showed late asthmatic re sponses to inhaled allergen (Dermatophagoides pteronyssinus). Each und erwent an exercise challenge test two days before (pre-allergen) and t wo days after (postallergen) an allergen inhalation challenge. FEV1 wa s measured at regular intervals up to ten hours after each challenge. Methacholine PC20 was measured before the allergen challenge and befor e the postallergen exercise challenge. Results: After the pre-allergen exercise test, all the subjects showed isolated early asthmatic respo nses. After the postallergen exercise test, seven showed dual response s (early and late asthmatic responses) (group I) and the remaining ten showed isolated early asthmatic responses (group II). Bronchial respo nses to pre-allergen exercise or inhaled allergen and the severity of early asthmatic responses to postallergen exercise were similar in gro ups I and II. Neither before allergen inhalation nor before the postal lergen exercise was methacholine PC20 different between the two groups . Methacholine dose shift caused by allergen challenge, however, was s ignificantly greater in group I than in group II (-2.00 +/- 0.39 versu s -1.36 +/- 0.53 doubling doses; P < .05). There was significant corre lation between the dose shift and the magnitude of late response to th e postallergen exercise in the whole group (r = 0.51, P < .05). Conclu sion: Late asthmatic responses to exercise may develop in some childre n with asthma following a late asthmatic response to allergen. This ph enomenon was related neither to the baseline nor to postallergen metha choline PC, but to the extent of increased sensitivity to methacholine caused by allergen challenge.