Your bronchial tubes carry air to and from your lungs, and bronchitis is an inflammation of the lining of those tubes. It is common for people with bronchitis to cough up thickened mucus, which can be discolored. It is possible to have acute or chronic bronchitis. The most common cause of acute bronchitis is a cold or other respiratory infections. Smoking often contributes to chronic bronchitis, which is an irritation or inflammation of the bronchial tubes' lining. Chest colds, or acute bronchitis, usually clear up within a week to ten days without lasting effects, though the cough may persist for some time. Chronic bronchitis, on the other hand, requires medical attention if you have repeated bouts of bronchitis. One of the conditions involved in chronic obstructive pulmonary disease (COPD) is in fact chronic bronchitis. The most common cause of chronic bronchitis is smoking tobacco, but it is not always the case. Secondhand smoke, air pollution, dust, or toxic gasses can also cause it. A family history of bronchitis, asthma, allergies and gastroesophageal reflux disease (GERD) can increase your risk.