It is a chronic inflammatory disorder of the airway in the lungs in which many cells and cellular elements play a role.  This inflammation causes recurrent episodes of wheezing, breathlessness, chest lightness, coughing particularly at nigh and in the early morning. The constriction of respiratory tract and inflammation is caused by three main

 

 

 

factors

 

 

The bronchial muscle next to each bronchial tube contracts causing a stifling or spasm and the inability to breath deeply and easily.

 

Accumulation of mucous in the bronchial tube

 

Inflammation of the mucous membrane in bronchial tube or a combination of the three.