Asthma 2

Part I of Essay
Asthma {az'-muh} Asthma is a respiratory disorder marked by breathing difficulty caused by temporary narrowing of the bronchi, the airways branching from the trachea to the lungs. Attacks usually are brought on by allergic reaction to ANTIGENS such as grass and tree pollens ....

Part II of Essay
.... asthma, however, the attacks become less frequent and less severe, but recovery between them is less complete. The bronchi in such patients become chronically narrowed, causing a progressive loss of capacity for physical exertion. The prevalence of asthma is only about 1 or 2 percent worldwide but varies greatly from country to country. In the United States, asthma affects about 6.9 percent of children. Typically, an asthma attack begins within minutes after exposure to a triggering agent. Symptoms include a sensation of tightness in t ....