On the basis of allergic tissue changes one can interpret the factors responsible for the signs and symptoms of allergic bronchial disease and evaluate the various therapeutic measures available for their control. In the pathology of allergic diseases two types of tissue changes are observed: (1) the reversible and (2) the irreversible.
REVERSIBLE TISSUE CHANGES
The reversible tissue changes, which are induced by such antigens as pollens, epidermals, foods, serums and drugs, are characterized by edema, smooth muscle spasm and stimulation of glands. Only the conducting portion of the lungs or bronchial tree is affected by the reversible tissue changes that account for the signs and symptoms of bronchial allergic disease.1Edema of the peribronchial tissues produces rigidity of the bronchial tree that interferes with the normal expansile and contractile movements of these structures,2 while swelling of the mucosa encroaches on the lumens, which are also narrowed by