Dear Doctor, Following a recent cold I have a persistent cough which has not responded to antibiotic treatment. Why is this?

There are many things that can cause coughs, but the overwhelming causes are as a result of colds. Colds are caused by viruses. These viruses cause inflammation of the respiratory tracts, which of course, involve not only the lungs but the nose, nasopharynx, sinuses, the Eustachian tubes, the canals which lead to the middle ear cavities that lie behind the ear drum leading to blocked noses, headaches, deafness and a cough.

Treating cold viruses with antibiotics does not work because viruses are not affected by these substances. However the inflammatory process itself, whilst meant to protect the highly specialized mucosa actually causes them to become more vulnerable to infection by bacteria living in the respiratory system. When this happens, the mucus, which is clear during the early part of the cold becomes yellow or green because of the resulting pus caused by this so called secondary infection. It is this part of the cold which can be effectively treated with antibiotics.

In vulnerable people it is best to reduce the early inflammation with specific medication given at the same time as the antibiotics.

In fit people with a strong immune system the body will be able to cope with the early viral illness and the secondary bacterial infection and the body will recover without active treatment. If signs and symptoms persist then see your Doctor for advice and if necessary, treatment.

Sometimes the cause of a cough can be more serious than a simple viral infection or complications may develop, for example pneumonia. Therefore you should see your Doctor if you:

• Cough up blood
• Become short of breath or wheezy
• Feel confused or drowsy
• Have chest pains headaches or fever that are worsening or severe
• Have a cough that persists for more than 3-4 weeks
• Have any other symptoms that are worrying you
• Have any pre-existing serious lung disease
• Are concerned about Swine Flu