Asthma is an inflammatory disease of the airways in the lungs. These airways are very sensitive and swell up in response to certain triggers. The muscles in the airways tighten and the airway lining becomes swollen and inflamed, producing sticky mucous. These changes cause the airways to become narrow, making it difficult to breathe and causing typical asthma symptoms such as coughing, wheezing, chest tightness and shortness of breath.
Causes of asthma