Significance of late reactions after bronchial challenge with house dust mite.

Sixty-nine children with moderately severe perennial asthma were submitted to bronchial provocation tests using aqueous extracts of Dermatophagoides pteronyssinus (house dust mite). 60 (87%) had immediate positive reactions. 73% also had late reactions occurring 4 to 8 hours after the challenge. A significant correlation was found between frequent attacks of asthma in the year before bronchial challange and the occurrence of late reactions. The late reaction was more prolonged and severe than the immediate reaction. The changes in lung mechanics during a late reaction were similar to those found in severe naturally occurring asthma. The possible relevance of the late reaction in antigen-induced asthma is discussed.