What is the difference between mucus and phlegm?
Mucus is a slippery secretion of the lining of various membranes in the body (mucous membranes). Mucus aids in the protection of the lungs by trapping foreign particles that enter the nose during normal breathing. Additionally, it prevents tissues from drying out. Increased mucus production in the respiratory tract is a symptom of many common diseases, such as the common cold. The presence of mucus in the nose and throat is normal, but increased quantities can impede comfortable breathing and must be cleared by blowing the nose or expectorating phlegm from the throat. Phlegm: the definition is limited to the mucus produced by the respiratory system, excluding that from the nasal passages, and particularly that which is expelled by coughing (sputum).
