Coughing is an automatic reaction to try to clear your airways. The airway may be partially blocked by phlegm (mucus), smoke, chemicals that you breathe in or a foreign body. Everyone will cough occasionally to 'clear their throat'.

What is a cough?

A cough is an automatic (reflex) muscle action that forces air up and out of your lower airways (lungs) and upper airways (windpipe, nose and mouth). You may cough to 'clear your throat' if you choke on food and it enters your windpipe instead of going down the food pipe (oesophagus). Or you may need to cough if you breathe in chemicals or smoke that irritate your airways. The cough reflex protects the airways of your lungs.

Cough affects us all if we need to clear our airways. Acute cough usually improves after one week. The most common cause is a viral infection which causes a runny nose and cough. Viral infections can affect anyone. However, young children commonly have 5-6 viral infections a year, especially in the winter months. Chronic cough is common. 1-2 adults in 10 are affected.

What causes cough?

Common causes of acute cough (lasting less than three weeks)

• Upper respiratory tract infections. These are the most common cause of acute coughs. They are caused by infection with a germ (virus). They almost always get better within a week, without specific treatment. Symptoms may go on for up to three weeks.
• Lower respiratory tract infections. These are less common; they can lead to more serious lung infections such as bronchitis or pneumonia. They may be caused by infection with germs (viruses, bacteria or fungi).
• Asthma. This causes wheeze, breathlessness and cough at night, in cold air and during exercise. An infection with a germ can make symptoms of asthma much worse. This is called an exacerbation of asthma.
• Irritants - smoke or chemical fumes that you breathe in may irritate the airways.

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