Chronic bronchitis is a long-term, often irreversible respiratory illness. Those with chronic bronchitis have a daily mucus-producing cough that persists for at least 3 months a year, at least 2 years in a row. Bronchitis is an inflammation of the lining of the air passages. Bronchitis can be classified as acute or chronic. Acute bronchitis is a mild inflammation of the air passages of the lungs that clears up within a few days, often without treatment. Chronic bronchitis is a persistent, serious lung disease that requires ongoing medical care and can lead to gradual deterioration of the lungs. Many people with chronic bronchitis also develop another respiratory disease called emphysema.

Chronic bronchitis involves restriction of airflow in the air passages that worsens over time. This causes increasing difficulty in breathing and more sputum (mucus) production in the lungs. Chronic bronchitis is a form of chronic obstructive pulmonary disease (COPD), a serious health condition. The diseases that fall under the COPD umbrella all lead to some type of long-term airflow problem in the lungs. The most common COPD conditions are chronic bronchitis, emphysema, and chronic asthmatic bronchitis. These may occur by themselves, but often a person has more than one condition occurring at the same time.

Chronic bronchitis, like other COPD conditions, can have episodes where symptoms get worse very quickly. These episodes are called exacerbations, and they can vary in degree of severity. Exacerbations of chronic bronchitis can be triggered by upper- or lower-airway infections, such as colds or influenza. Exposure to environmental irritants, such as dust, fumes, or air pollution, may also exacerbate chronic bronchitis. Other medical conditions, such as heart problems or infection elsewhere in the body, can worsen chronic bronchitis symptoms. Exacerbations can be serious and even life threatening.