What causes coughing up phlegm?

Phlegm is mucus made by the airways to trap particles and germs. During acute bronchitis, irritated tubes may make extra mucus. Chronic sinusitis can let mucus drain down the throat and trigger coughing. Pneumonia may cause phlegm alongside fever, chest discomfort, or breathlessness. Bronchiectasis and COPD can produce frequent or persistent sputum because the airways clear mucus less effectively.

Clear, white, yellow, or green phlegm does not identify the cause by itself. A change from your usual pattern, foul-smelling sputum, or repeated chest infections should be assessed rather than judged by colour alone.

Drink fluids, rest, and avoid tobacco smoke, vaping, and dusty air. Gentle movement can help loosen mucus if you feel well enough. Do not use leftover antibiotics; a clinician decides whether antibiotic treatment is appropriate after considering symptoms and examination. If you have a long-term lung condition, follow your prescribed airway-clearance or inhaler plan and seek advice when your usual sputum changes.

Get urgent help for severe breathing difficulty, blue lips, confusion, chest pain, or blood in the phlegm. Arrange prompt review for high or persistent fever, worsening breathlessness, dehydration, new confusion, repeated infections, or phlegm that continues beyond an expected respiratory illness. People with COPD or other lung disease should follow their personalised flare-up plan.

Ask whether the phlegm fits an infection, sinus drainage, or a long-term airway problem, and whether you need a chest examination or a sputum sample. Share its colour and smell, how long it has been present, any fever or breathlessness, smoking history, and your regular medicines.