Phlegm

Phlegm is a water-based gel produced by the respiratory system in response to inflammation and infection, consisting of glycoproteins (such as mucins), immunoglobulins, lipids, cellular debris, and microbes. It is distinct from normal mucus due to its association with disease states. The color and consistency of phlegm provide clinical clues: yellow/green phlegm often signifies infection, clear phlegm may indicate allergies, and bloody or brown phlegm suggests more serious conditions, including malignancy or infection[1][3][5]. Phlegm is expelled from the airways via coughing (as sputum), and its production is increased in respiratory tract infections, chronic pulmonary diseases, and allergic reactions. Excessive, persistent, or bloody phlegm should be medically evaluated[1][5].

Other names

sputumrespiratory mucusmucus