Late bronchial obstructive reaction to experimental inhalation of house dust extract

Summary This study was undertaken to confirm the high incidence of the ‘late’ bronchial reaction after house dust inhalation and to assess whether symptoms and signs of these ‘late’ reactions were comparable with the clinical features of the classic Type III (Gell and Coombs) allergic reactions in the lung as shown by extrinsic allergic alveolitis. Although the time sequence of this late reaction is in agreement with the classic Type Ml reaction (Arthus phenomenon), other features of alveolitis are absent. There were no crepitations on physical examination, no fever, no leucocytes, no decrease of the PaO 2 , and no abnormal radiological findings. These results were related to the protective effects of some drugs. The protective effect of disodium cromoglycate and prednisolone is probably the same in both types of late reactions. The protective effect of antihistamine drugs, which is found in this late obstructive reaction, is, according to the literature, absent in the classical Type III reaction. There seem to be no valid arguments to ascribe the ‘late’ bronchial obstructive reaction to the toxic complex syndrome. Theoretical and practical implications of the late obstructive bronchial reaction are mentioned.