Asthma is a chronic inflammation of the airways, which causes swelling and narrowing (constriction) of the airways. The result is difficulty in breathing. The bronchial narrowing is usually either totally or at least partially reversible with treatments. Lung airways that are chronically inflamed may become overly sensitive to allergens (specific triggers) or irritants (nonspecific triggers). The airways may become “twitchy” and remain in a state of heightened sensitivity.