Cough is a common symptom of upper respiratory tract infection (URTI) and lung disease. A cough may be productive, where the patient coughs up sputum, or non-productive, where there is no sputum. A productive cough is often described as loose and a non-productive cough as dry. Sputum (or phlegm) may be clear or white (mucoid), yellow due to the presence of pus (purulent), or blood-stained (as in haemoptysis).

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