Phlegm

Phlegm is a form of mucus produced by the mucous membranes of the respiratory tract, including the nose, throat, and lungs. It serves to trap dust, microbes, and other particles, and is normally cleared by cilia toward the throat to be swallowed or expelled. The production of mucus increases during irritation, infection, or inflammation, leading to the accumulation of phlegm that may be coughed up.

Physiologically, phlegm consists mainly of water, glycoproteins, salts, and immune components such as antibodies, with cellular debris from damaged cells. Its color and consistency can vary: clear or white mucus is common with viral infections or allergies; yellow or green mucus may reflect an inflammatory response or bacterial involvement; blood-tinged mucus can occur with irritation or more serious conditions. Persistent changes in color, thickening, or foul odor, or mucus associated with fever, chest pain, or breathing difficulty, warrant medical evaluation. Common sources of increased phlegm include viral infections such as the common cold, bronchitis, asthma, chronic obstructive pulmonary disease, smoking, and environmental irritants.

Management is typically supportive and condition-specific. It often includes adequate hydration, humidified air, and saline rinses or gargles to loosen mucus. Depending on the cause, treatments may involve medications that thin or loosen mucus (expectorants or mucolytics), inhaled therapies for airway conditions, or treatment of underlying infections or irritants. Seek medical advice if phlegm lasts several weeks, becomes persistently thick, is blood-tinged, or is accompanied by chest pain, shortness of breath, or high fever.