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What is asthma?
Asthma is an obstructive lung disease, characterized by reversible constriction of the small airways, mucosal inflammation and edema, and increased mucous secretions. Attacks are characterized by episodes of shortness of breath or wheezing lasting minutes to hours. Between attacks there is an absence of symptoms. Exacerbations are periods of increased airway reactivity. Both attacks and exacerbations are often precipitated by allergic causes (pollen, dust) or by airway irritation (smoking, pollution, cold, respiratory infections). Local trigger factors (leukotrienes, prostaglandins) are released and contribute to inflammation, while vagal stimulation plays a role in bronchoconstriction.
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