What Causes Bronchitis?

Acute Bronchitis

Infections or other factors that irritate your lungs cause acute bronchitis. The same viruses that cause colds and the flu are the most common cause of acute bronchitis. Sometimes bacteria can cause the condition.

Certain substances can irritate your lungs and airways and raise your risk for acute bronchitis. For example, inhaling or being exposed to cigarette or cigar smoke, air pollution, dusts, vapors, or fumes raises your risk. These lung irritants also can make symptoms worse.

Being exposed to a high level of dust or fumes, such as from an explosion or a big fire, also may lead to acute bronchitis.

Chronic Bronchitis

Repeatedly breathing in fumes that irritate and damage lung and airway tissues causes chronic bronchitis. Smoking is the major cause of this condition.

Breathing in air pollution and dust or fumes from the environment or the workplace also can lead to chronic bronchitis.

People who have chronic bronchitis go through periods when symptoms become much worse than usual. During these times, they also may have acute viral or bacterial bronchitis.