Asthma (Az-muh) is a chronic disease that affects the airways of millions of Americans. The airways are the tubes that carry air in and out of your lungs. If you have asthma, the inside walls of your airways become swollen and inflamed in reaction to irritants.  When the airways react, they get narrower, and less air flows through to your lung tissue. This causes symptoms like wheezing (a whistling sound when you breathe), coughing, chest tightness, and trouble breathing, especially at night and in the early morning.

Asthma cannot be cured, but most people with asthma can control it so that they have few and infrequent symptoms and can live active lives.