clipped from www.nhlbi.nih.gov

What Is Asthma?

Asthma (Az-muh) 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
(swollen). The inflammation (IN-fla-MAY-shun) makes the airways very sensitive,
and they tend to react strongly to things that 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 (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.