Bronchial provocation studies in farmers with positive RAST to the storage mite Lepidoglyphus destructor

Bronchial provocation studies with L. destructor (L. des.) extract were made on 12 farmers with asthma who were exposed daily to stored hay and grain and had positive radio-allergo-sorbent test (RAST) to L. des. All 12 farmers developed more than a 20% fall in FEV1 to the extract. None of the symptomatic farmers who were also RAST positive to the L. des. culture medium developed an asthmatic reaction to the medium extract. Neither four healthy farmers nor two patients with asthma caused by D. pteronyssinus (D. pt.) responded to L. des. or the L. des. culture medium. Challenges with D. pt. extract were negative in two symptomatic farmers who were RAST positive to L. des. and negative to D. pt. The present study further supports our previous hypothesis that there is an IgE-mediated immunological mechanism behind L. des.-induced asthma in farmers and that atopic farmers are liable to develop occupational asthma caused by allergy to L. des..