Black mucus is rare. It can be the sign of a fungal infection, or exposure to pollutants such as coal, dust or cigarette ...

Clear, bubbly phlegm does not typically indicate a problem. However, coughing up large amounts could indicate an underlying health issue, such as fluid in the lungs. Phlegm, or sputum, is a type of ...

It is not unusual to cough up phlegm with a common cold. However, it can also indicate a different, sometimes serious, underlying condition such as stomach acid reflux, lung disease, or heart disease.