Comparison of responses to pollen extract in subjects with allergic asthma and nonasthmatic subjects with allergic rhinitis

Abstract We compared pulmonary responses with inhaled pollen-antigen extract in eight subjects with allergic asthma and eight nonasthmatic subjects with allergic rhinitis. Lower respiratory tract sensitivity to antigen was determined from dose-response curves using SGaw and FEV 1 measurements to quantitate responses. We found no difference in antigen sensitivity in terms of SGaw between the two groups (p > 0.05). Hay fever subjects required almost eight times more antigen to produce a 20% fall in FEV 1 , although there was considerable overlap between the two groups. After antigen challenge there were significant increases in lung volumes in asthmatic subjects (RV, +78.6%; FRC, +33.6%; TLC, +12.6%) which were not significantly different from rhinitis subjects (RV, +98.3%; FRC, +39.1%; TLC, +10.3%). Six rhinitis and five asthmatic subjects were rechallenged after pretreatment with atropine (2.5 mg aerosol). Atropine caused an initial increase in SGaw and FEV 1 but failed to alter sensitivity or volume responses in both groups. The effects of a maximum inspiration on physiologic responses to antigen were different in the two groups. Deep inspiration transiently improved SGaw and FRC toward prechallenge values in rhinitis subjects but the same maneuver had little effect in asthma subjects. Although only asthma subjects experience lower respiratory tract symptoms during periods of environmental pollen exposure, these two groups of subjects were indistinguishable on the basis of their immediate responses to inhaled antigen. This suggests that asthmatic symptoms during the pollen season are unrelated to the immediate effects of allergic reactions to pollen. This also suggests that these bronchial challenge responses represent a localized anaphylactic reaction, whereas naturally occurring asthma during the pollen season may represent a syndrome of increased airways reactivity which is perhaps related to antigen exposure.