What causes bronchitis?
Acute bronchitis often develops after having a cold or the flu. It is most commonly caused by a virus, such as the influenza virus, but can also be caused by bacteria and other particles, such as air pollution or chemicals that are breathed in and irritate the lining of the airways. These factors cause the lining of the large airways, called bronchi, to become inflamed and swell up. They also cause the airways to produce more mucus than usual, which your body tries to get rid of by coughing.