Bronchitis is the inflammation of the mucus membrane of bronchial tubes (or bronchi), the air passages that extend from the trachea into the small airways and alveoli.
It affects children and adults mostly in winter, especially during outbreaks of influenza.
It is commonly caused by infections, cigarette smoking and inhalation of environmental pollutants. These agents cause inflammation of the airways and secrete thick mucus or phlegm causing the characteristic cough of Bronchitis, wheezing, and shortness of breath.
Bronchitis can become serious in elderly people, chain smokers or those who are chronically ill with heart or lung diseases.