The pathogenesis of asthma can be divided into clinical, physiological, and anatomical considerations. Clinical features include reversible obstruction, allergens, and other factors such as gastroesophageal reflux. Physiological considerations include bronchial hyperreactivity, neurologic abnormalities, nonadrenergic noncholinergic system (NANC), and neuropeptides. Anatomic and cellular considerations include eosinophils, respiratory epithelium, mast cells/basophils, cytokines, and histamine-releasing factors (HRF), and histamine-release inhibitory factor (HRIF).