Asthma is a chronic condition involving the respiratory system in which the airways occasionally constrict, become inflamed, and are lined with excessive amounts of mucus, often in response to one or more triggers. These episodes may be triggered by such things as exposure to an environmental stimulant such as an allergen, environmental tobacco smoke, cold or warm air, perfume, pet dander, moist air, exercise or exertion, or emotional stress. In children, the most common triggers are viral illnesses such as those that cause the common cold.
This airway narrowing causes symptoms such as wheezing, shortness of breath, chest tightness, and coughing. The airway constriction responds to bronchodilators. Between episodes, most patients feel well but can have mild symptoms and they may remain short of breath after exercise for longer periods of time than the unaffected individual. The symptoms of asthma, which can range from mild to life threatening, can usually be controlled with a combination of drugs and environmental changes.
In asthma, constriction of the airways occurs due to bronchoconstriction and bronchial inflammation. Bronchoconstriction is the narrowing of the airways in the lungs due to the tightening of surrounding smooth muscle. Bronchial inflammation also causes narrowing due to oedema and swelling caused by an immune response to allergens.
Inflamed airways and bronchoconstriction in asthma. Airways narrowed as a result of the inflammatory response cause wheezing.
When an asthma attack is unresponsive to a patient's usual medication, other treatments are available to the physician or hospital:
Asthma is usually diagnosed in childhood. The risk factors for asthma include:
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