Phlegm (//; Greek: φλέγμα"inflammation,
humour caused by heat") is a liquid secreted by the mucous membranes ofmammalians. Its definition is limited to themucus produced by the respiratory system, excluding that from the nasal passages, and particularly that which is expelled by coughing (sputum). Phlegm is in essence a water-based gel consisting of glycoproteins,immunoglobulins, lipids and other substances. Its composition varies depending on climate, genetics, and state of theimmune system. Its color can vary from transparent to pale or dark yellow and green, from light to dark brown, and even to dark grey depending on the constituents.
Distinction between
mucus and phlegm