Mucus is a thin, slippery fluid that lines the nose, throat, and other passages to trap dust and germs. Phlegm is a thicker type of mucus produced in the lungs to catch and remove harmful particles ...

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 ...