Bronchitis is an inflammation of the lining of your bronchial tubes, which carry air to and from your lungs. People who have bronchitis often cough up thickened mucus, which can be discolored. 

Acute bronchitis is often caused by a viral respiratory infection and improves by itself.

Symptoms of bronchitis include coughing up thickened mucus and shortness of breath. Cough can be dry, or with phlegm. Person will experience fatigue or malaise, runny nose or post-nasal drip, chest pressure, headache, sleeping difficulty, or sore throat. Wheezings.