A person with chronic bronchitis has swelling and irritation of the air passageways in the lungs.

The inside surface of the passageways become swollen and produce mucus. The combination of swelling and mucus narrows the passageway, which can reduce airflow. Common causes of chronic bronchitis include smoking and asthma. Bronchitis becomes chronic when the air passageways do not heal completely, and symptoms continue despite treatment.

Many people with chronic bronchitis also suffer from chronic obstructive pulmonary disease or COPD.