A cough can be annoying – to the person suffering from it and those around them – and it is an irritation of the airways that causes it. This irritant might be something in the atmosphere or deliberately inhaled; or a microorganism, such a bacterial or viral infection, but in all cases it stimulates receptors in the larger airways that then send a message to the medulla in the brain – note that this is also the location that regulates breathing – which in turn triggers an involuntary reflex, located in the pharynx: cough. It is also possible to deliberately cough, so there is sometimes a voluntary element to the action.

It is important to bear in mind that the irritant causing a cough may not be obvious. Some examples include asthma that is poorly controlled; a small amount of mucus running down the back of the throat after another condition seems to have cleared, which is known as postnasal drip; acid reflux from the stomach; or as a side effect of medication, particularly a class of blood pressure drugs called ACE inhibitors.

Classifying coughs

Coughs are classified in a couple of different ways:

Dry or chesty?

A dry cough may also be described as tickly or non-productive, whereas phlegm is present in a chesty or productive cough and is the body’s way of trapping and removing particles and physical irritants from the airways. For this reason, it is important to not suppress a productive cough.

Acute or chronic?

A cough that has been present for less than three weeks is regarded as acute, whereas one that is more persistent – particularly if it lingers for longer than eight weeks – is termed chronic.

It is important to try and get a full picture when someone complains of a cough, including how long they have had it, any other conditions they have or medicines they are taking, smoking and occupational history, recent illnesses, whether it is worse at night or during the day, and any other symptoms.