Asthma causes and symptoms
Tightening, inflammation, and increased mucus production in the airways characterize asthma. In people with asthma, the airways are very sensitive and react to a variety of "triggers." Coming into contact with these triggers is what causes the airways to tighten and become inflamed and blocked with mucus, resulting in problems breathing, asthma symptoms, or worsening of asthma symptoms. A severe asthma attack can begin immediately after exposure to a trigger or several days or weeks later. ... Recognizing and avoiding these triggers, when possible, is an important way to control asthma. The most common asthma triggers: Upper respiratory infections: cold and flu, bronchitis (infection of the large airways), or sinus infections.