Asthma is a disease of the lungs in which the airways become blocked or narrowed causing breathing difficulty. This chronic disease affects 20 million Americans. Asthma is commonly divided into two types: allergic (extrinsic) asthma and non-allergic (intrinsic) asthma. There is still much research that needs to be done to fully understand how to prevent, treat and cure asthma. But, with proper management, people can live healthy and active lives.