Asthma is a chronic inflammatory disease of the airways that is characterized by variable narrowing of the airways and symptoms of intermittent dyspnea, wheezing, and nighttime or early-morning coughing.

 

Asthma is a major health problem throughout the world, affecting an estimated 315 million persons of all ages. Asthma is clinically heterogeneous, and its pathophysiology is complex.Airway eosinophilic inflammation is typical, but many patients with mild asthma have persistently noneosinophilic disease.Airway hyperresponsiveness is a consistent feature; irreversible airflow obstruction develops in some patients, presumably as a consequence of remodeling of the airway wall.

 

Short periods of loss of asthma control may occur as a result of exposure to nonspecific “triggers,” such as fumes, strong smells, or exercise. Moderate or severe exacerbations are usually due to exposure to allergens or viruses, particularly human rhinovirus.