Cough is a reflex stimulated by irritation of the lungs, the trachea or the pharynx. It is often a reaction to infection or contamination (e.g. dust or pollen) and is a protective mechanism to clear the airways. The most common cause is an infection such as the common cold.

A dry cough or non-productive cough as the name suggests does not produce any phlegm and is tickly and tight. The cause is unlikely to be bacterial. It is a response to a viral infection, smoking, air pollution or a change in temperature.

A chesty or productive cough produces sputum. Thick yellow, green or brown sputum suggests a lower respiratory infection.

Croup is a harsh bark in infants with the cough often occurring in bouts and the child often has difficulty in breathing and a noise in the throat on inhaling.