The airflow obstruction is usually reversible, either spontaneously, or through pharmacologic therapy.
Symptoms of asthma are typically paroxysmal or episodic and include coughing, wheezing, and dyspnea.
Allergic or extrinsic asthma is the most common form of asthma and most frequently occurs in children and young adults. The etiology of extrinsic asthma is believed to be a manifestation of type I hypersensitivity localized to the airways, and is mediated by the interaction of various external allergens, sensitized IgE antibodies, and proinflammatory mast cells which line the tracheobronchial tree. Binding of the allergens to sensitized IgE attached to the surface of mast cells triggers their degranulation and the release of histamines, bradykinins, leukotrienes and prostaglandins. Intrinsic asthma typically appears first during adulthood and its onset if frequently associated with an upper respiratory infection. The pathogenesis of intrinsic asthma is not well understood.