Difficulty in breathing caused by a sudden constriction of the muscles in the wall of the bronchi. A feature of asthma, chronic bronchitis and anaphylaxis. The overactivity of the bronchus muscle is as a result of exposure to a stimulus (trigger) which under normal circumstances would cause little or no response. The resulting constriction and inflammation causes a narrowing of the airways and an increase in mucous production this reduces the amount of oxygen that is available to the individual causing breathlessness, coughing and cyanosis.

--Tam 14:01, 10 May 2004 (UTC)