Bronchitis is a condition where the lining of bronchial tubes (bronchi), becomes inflamed, swollen, or infected. Bronchitis is generally caused by bacteria, viruses, es, and other particles that create irritation in the bronchial tubes. The bacterial infection can be caused due to exposure to substances like dust, air pollution, fumes, tobacco, etc., which irritates the lung greatly. The viral infection, on the other hand, is most of the time caused due to the same viruses that cause cold and flu.