Cough is a forced expulsive manoeuvre usually against a closed glottis, which is associated with a characteristic sound. It usually has a protective function in maintaining patency and cleanliness of the airways.

The impact of cough on patients and relatives is often underestimated. Patients may need symptomatic treatment when cough is persistent, distressing or affecting sleep and/or quality of life. An assessment of the pattern and character of the patient's cough is essential to optimise treatment. Acute cough is defined as duration of <3 weeks, sub-acute as 3 to 8 weeks, chronic as >8 weeks. For information on the nature of cough, refer to the Management section.