Asthma

Asthma is a chronic disease of the airways, the branching tubes that carry air into and out of the lungs. In people with asthma the airway lining is persistently inflamed and overly sensitive. When it meets a trigger, the smooth muscle around the airways tightens, the lining swells and extra mucus is made, so the passages narrow and air struggles to get through, especially on breathing out. The narrowing usually eases again, on its own or with treatment.

Symptoms include wheezing, a cough that is often worse at night or early in the morning, shortness of breath and a tight chest. They come and go, and a sudden severe flare is called an asthma attack. Common triggers include allergens such as pollen, dust mites and animal dander, respiratory infections, cold air, exercise, smoke and air pollution. Doctors confirm the diagnosis with lung function tests such as spirometry.

Asthma cannot be cured, but it can usually be controlled. Bronchodilator inhalers act quickly to open the airways during symptoms, and daily inhaled corticosteroids calm the underlying inflammation and lower the risk of serious attacks. It affects people of all ages, and hundreds of millions of people live with it worldwide.