What is asthma?

As we breathe, air moves in and out of the lungs through branching airways. People with asthma have sensitive airways, which become narrowed as a result of many causes. This makes it difficult for them to breathe.

The three main factors that cause this narrowing of the airways are:
The inner lining of the airways becomes red and swollen, the muscle around the airways tighten and extra mucus may be produced.