Inflammation from infection or irritation damages the cells that line the airways. When the cilia stop working, the air passages become clogged with debris, which increase the irritation even more. As the irritation continues, the airways become more vulnerable to further infection and tissue damage. Bronchitis may be acute or chronic. However, bronchitis may start on its own as well, without any prior infection.
Chronic bronchitis lasts three months or more, and symptoms can return year after year.
Chronic bronchitis can be life-threatening. The condition may result from a series of acute bronchitis attacks, or it may develop gradually because of heavy smoking or inhaling polluted air. This makes antibiotic therapy unlikely to be of help since these drugs can only affect bacterial illnesses and cannot eradicate viral illnesses or irritants. Additionally, a type of asthma which produces little wheezing but considerable amounts of cough is often misdiagnosed as acute bronchitis. Avoiding irritants, maintaining good nutrition and being patient are the most effective therapies for most cases of bronchitis.