Immunotherapy in cat-induced asthma. Double-blind trial with evaluation of bronchial responses to cat allergen and histamine.

Ten asymptomatic patients with normal pulmonary function were selected for a double-blind trial of immunotherapy in cat-induced asthma. Each patient had a positive prick test to cat pelt extract and also a positive bronchial challenge response to the same extract. Patients were randomly assigned to active treatment or placebo groups and received weekly or biweekly injections over a 3 to 4-month period. The 5 patients who received the active treatment received a cumulative dose of cat pelt extract that ranged from 16.4 to 44.8 mg of total solid containing 1.7 to 4.7 mg of cat allergen 1. Apparent systemic reactions were observed in 3 patients who received the placebo and 3 patients who received the active treatment. The 5 patients who received the active treatment showed a reduction in skin reactivity to cat pelt extract as well as a significant mean reduction in bronchial sensitivity to the same extract. The 5 patients who received the placebo showed no significant changes in skin reactivity or bronchial sensitivity to cat pelt extract. Bronchial response to histamine did not change significantly in either the active treatment of the placebo group.