Late airway response increases at repeat allergen challenge

The relationship between the immediate and late responses to repeated inhalations of allergen was studied. Sixteen male atopic asthmatics were challenged twice with an interval of 2 weeks. Forced expiratory volume in 1 s (FEV 1 ) was measured serially over an 8‐hour period after challenge. The method of provocation used implied that only slight differences between the immediate responses on the two provocation days were observed. However, differences in the late responses were demonstrated. Thus, the maximum percent change in FEV, at the first and second provocation differed significantly in the late ( P < 0.01), but not in the immediate phase. The increase in maximal late response was greater than the small change in maximal immediate response ( P < 0.05). Further, the FEV 1 values from 4 to 8 h post‐challenge were in each recording significantly lower on the second day suggesting a more pronounced late bronchial response to repeat challenge. The results suggest that after one challenge specific airway reactivity, i.e., reactivity to allergen, at a subsequent rechallenge is increased in the late phase. This late phase hyperreactivity seems to persist for at least 2 weeks after allergen provocation.