Asthma is a chronic disease that affects your airways. The airways are the tubes that carry air in and out of your lungs. If you have asthma, the inside walls of your airways are inflamed or swollen. The inflammation or swelling makes the airways very sensitive, and they tend to react strongly to things you are allergic to or find irritating. When the airways react, they get narrower, and less air flows through to your lung tissue. This causes symptoms like wheezing, 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.