REPEATED AEROSOL EXPOSURE TO SMALL DOSES OF ALLERGEN - A MODEL FOR CHRONIC ALLERGIC-ASTHMA

To improve our understanding of the pathophysiology of chronic allergi c asthma, we mimicked natural allergen exposure by giving tiny doses o f dust-mite extract (equivalent to estimated daily exposure in a typic al bedroom) in three weekly sessions for 4 wk. Nine mild asthmatic adu lts who were highly sensitive to dust-mite allergen participated in th e study. Serial assessments of bronchial reactivity by methacholine ch allenge, pulmonary function, symptoms, and bronchodilator requirements were obtained. Seven of nine subjects had a twofold or more (median: 6, range: 2.7 to 25) reduction (p = 0.008) in PC20, after which saline inhalations were substituted for dust-mite extract. Bronchial reactiv ity returned to normal within 2 to 3 wk after cessation of dust-mite i nhalations in all but one subject. Predosing FEV1 dropped 10% over 4 w k of provocation (p = 0.001) and 7 of 9 returned to prestudy level wit hin 2 wk after dosing was stopped. Late-phase responses were seen in 6 of 9 subjects. We conclude that repeated aerosol exposure to dust-mit e allergen in doses comparable to natural bedroom exposure is sufficie nt to adversely affect pulmonary function and bronchial hyperractivity in sensitized individuals. These changes are rapidly reversible. This low-dose provocational strategy provides an attractive model for the experimental study of allergic asthma.