Factors influencing the occurrence of late bronchial reactions after allergen challenge

Forty-seven patients with allergic bronchial asthma were challenged with the relevant allergen. Forty-eight per cent of the provocations resulted in a positive immediate reaction followed by a late bronchial response. Late bronchial obstruction was more common among patients with a high than with a low RAST score. Ten patients were challenged with different allergens on two different occasions, but the same type of bronchial response was observed in only six of them. Nine patients with an isolated immediate response were rechallenged with higher allergen doses, the early bronchial response being partially counteracted by terbutaline inhalations in clinically appropriate doses before and during the inhalation of allergen. The treatment alleviated the early reaction in six of the patients. A late reaction occurred in all patients with an immediate response. The non-specific bronchial reactivity to methacholine was assessed in 24 patients before allergen challenge. No relation was found between this reactivity and the observed patterns of reactions to allergen. It was concluded that the occurrence of a late bronchial response probably depends on the dose of allergen administered but is independent of the degree of unspecific bronchial responsiveness to methacholine prior to the challenge.