Mechanism of perennial allergic asthma.

The early (immediate) allergic asthmatic response does not account for the clinical features of perennial asthma. However, the late response--now thought to be due to allergen-IgE reaction-and the increase in non-allergic bronchial reactivity that is seen in allergen-sensitive asthmatics and that follows the late response do suggest an explanation. If the increased non-allergic bronchial reactivity somehow enhances bronchial responsiveness to allergen there would, in perennial allergic asthma, be a vicious circle. It will not be easy to test, in the laboratory or clinically, the validity of this hypothesis, but there are important implications for diagnosis, treatment, and prevention.