Asthma

Asthma is a chronic disorder of the lungs in which inflamed airways are prone to constrict, causing episodes of breathlessness, wheezing, coughing, and chest tightness that range in severity from mild to life-threatening. Inflamed airways become hypersensitive to a variety of stimuli, including dust mites, animal dander, pollen, air pollution, cigarette smoke, medications, weather conditions, and exercise. Stress can exacerbate symptoms.

Asthmatic episodes may begin suddenly or may take days to develop. Although an initial episode can occur at any age, about half of all cases occur in persons younger than 10 years of age, with boys being affected more often than girls. Among adults, however, the incidence of asthma is approximately equal in men and women. When asthma develops in childhood, it is often associated with an inherited susceptibility to allergens, substances such as pollen, dust mites, or animal dander that may induce an allergic reaction. In adults, asthma also may develop in response to allergens, but viral infections, aspirin, and exercise may cause the disease as well. Adults who develop asthma may have nasal polyps or sinusitis.