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Asthma is a condition which causes the airways to narrow, often in response to a "trigger" such as exposure to something that causes an allergic reaction - cold air, exercise, or emotional stress. This narrowing causes symptoms such as wheezing, shortness of breath, chest tightness, and coughing, which respond to drugs known as bronchodilators. Between episodes, most patients feel fine.
The disorder is a chronic (recurring) condition in which the airways become very sensitive to irritation. Asthma causes inflammation, increased mucus production, and intermittent airway obstruction. The symptoms of asthma, which can range from mild to life threatening, can usually be controlled with a combination of drugs and lifestyle changes.
Public attention in the developed world has recently focused on asthma because it seems to be on the increase, affecting up to one in four children who live in cities.
Susceptibility to asthma can be explained in part by genetic factors, but no clear pattern of inheritance has been found. Asthma is a complex disease that is influenced by multiple genetic, developmental, and environmental factors, which interact to produce the overall condition.
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