Why do we suffer pain? Normally pain is a warning that something in the body is wrong. It draws our attention to it so that we take appropriate action, for example a cut on the skin or a toothache. If we did not experience pain we would damage ourselves without knowing it.

Doctors and patients wish to know the cause of any pain. In some cases this is obvious, in others extensive investigations may be required to make a diagnosis. The cause of the pain can then be treated and the pain goes away. This is the normal experience of the vast majority of patients.

Unfortunately, things are not always so simple. In many cases even though the cause of the pain is known, for example some types of arthritis, the initial cause may not be reversible and pain becomes chronic or long lasting. In other cases the cause of the pain cannot be identified at all but the patient is still in pain.

Pain is an unpleasant sensory experience. The source of the pain may vary enormously. It may be due to injury, infection, inflammation or cancer. Nerve endings in the vicinity of the painful area are stimulated mainly by special chemicals released by the body in response to the above. 

Electrical impulses are carried by the nerves to the spinal cord and up to the brain where they are interpreted as pain. The pain may be well localised as for instance a boil on the skin, or in the case of internal organs, much more diffuse and variable, for example angina in heart disease.

Most painkilling drugs work by blocking these nerve impulses at some point in their journey from the peripheral site to the brain. Thus aspirin and other anti-inflammatory drugs like nurofen work near the site of the pain and drugs like codeine and morphine work at spinal cord and brain level.

Normally, the nerves act merely as telephone lines to relay pain in the body and tell us something is wrong.

However, when nerves are damaged themselves, they can create pain which arises from within the nerve itself. Doctors call these pains neuropathic pains. They are more difficult to relieve because the usual painkilling drugs are ineffective.