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Pain and how it works

Pain is a sensation that is universal and experienced by all of us at some time or another.  Everyone has experienced different types of pain at different times and for different reasons. On this part of our site, you can learn about different aspects of pain in more detail, including the science behind how pain works.  Understanding this will help you to understand you pain and may make it easier for you to manage, and to understand some of the things that are done to try to reduce it.


Chronic pain is a very common condition with a massive impact in the UK and worldwide.  This is discussed further in the "impact of pain" page.

Those involved in caring for people with pain have been pleased that in recent years the NHS and Government have begun to treat pain as a more serious issue, with the Chief Medical Officer and others stating the management of pain to be a high priority.


What is pain?

The International Association for the Study of Pain (IASP) defines pain as

"An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage".

It has more simply been summed up as “what the patient says hurts”.

The IASP definition is useful, since it stresses two aspects of pain.  Pain is something that you feel physically – your body senses it. We know a great deal about the physical aspects of pain.  However, as well as this, pain is also something you feel emotionally. Pain is subjective, affected by your current and past experiences, your individual bodily response to pain and what the pain means to you. It is also affected by psychological factors from day to day. For example, on days that you are feeling down, you may notice pain more than on days when you are feeling happy.  We also all notice times when we can distract ourselves from pain and notice it less.  So it can sometimes be hard for doctors to understand exactly what you are feeling with your pain.  Many patients, sadly, can be given the impression that doctors and others feel that the pain is "all in their head".  We feel that this (if it even exists) is incredibly rare and is unhelpful.  Ronald Melzack, who co-wrote the influential gate control theory of pain, very appropriately said:

“The term 'psychogenic' assumes that medical diagnosis is so perfect that all organic causes of pain can be detected; regrettably, we are far from such infallibility... All too often, the diagnosis of neurosis as the cause of pain hides our ignorance of many aspects of pain medicine.”


Acute and Chronic Pain - is pain always bad?

Pain can be described as Acute and Chronic, depending on its duration. Acute pain is of short duration and normally self-limiting, for instance after injuries or operations.  Pain can become Chronic or long-lasting.  

Acute pain is your body’s way of saying that something is or might become damaging to you. It is a warning sign, in the same way as a fever tells you that you are ill (that something is already wrong) and a fire alarm tells you your chip pan has caught fire (that you might have a problem if you don’t do something about it).

Acute pain is generally sudden in onset, and lasts a relatively short time. It is often an “emergency” pain signal. If you turn on a tap and put your hands under it, and the water that comes out is painfully hot, you will immediately pull your hands away. The pain warned you that if you continued to keep your hands in the water, they would probably get badly burned. As another example, your shoe may rub against your foot, causing you pain but no injury. If you ignore this warning sign, you can end up with a blister – damaged tissue – as well as pain. Acute pain generally disappears when the injury heals or the illness goes away (either of its own accord, or after successful treatment), or the body can no longer detect the source of the pain (for example, your rubbing shoe).

If people cannot feel pain, as happens for instance in Leprosy, they lose the protective messages that warn of harm.  The well-known damage that happens to the hands and feet in leprosy is not becuse of the disease, but because of repeated damage and injury from cuts, burns and similar trauma, the pain from which is not felt by the person with the disease. 

Sometimes pain can become chronic, or persistent.  This pain may range from mild to severe. It is said to be chronic when it is present to at least some degree for long periods of time. This time is often arbitrarily defined as six months though this is not very helpful, and often many of the properties of chronic pain can develop rapidly after its start. 

Chronic pain may remain constant, or it can come and go, like the pain of migraines. It sometimes indicates a long-lasting health problem, which may or may not be serious and may or may not be treatable.  These may be due to causes such as wear and tear of joints: this is called nociceptive pain.  Sometimes changes in the nervous system can themselves lead to pain: this is called neuropathic pain.  Indeed, sometimes pain itself can cause changes in the nervous system that lead to increased and persisting pain sensation.  

The problem may go away (resolve) with time, or the pain may be something that the person has to live with for the rest of their life. If this is so, the pain can grow from being one of many symptoms, to the main problem.  

Pain, whether or not it is severe, can be so distracting that it prevents us from completing our daily tasks without constantly having to stop, and it can cause considerable suffering and impact on our whole lives.

Further pages in this section will discuss how we feel pain and how it works, and some other aspects of pain, and can be accessed from the menu on the right.


Further reading

We would very highly recommend a very useful book produced by the British Pain Society on Understanding and Managing Pain which you may find helpful.  This booklet has been produced to help patients understand and manage their pain. Whether the pain is recent or long-term, severe or less severe, this booklet explores how to get the best out of the patient and healthcare professional partnership. It looks at what pain is, what can be done about it and who can help.

This document can be downloaded free of charge by clicking this link

BPS booklet 

A useful slide presentation from Owen Hughes, a specialist psychologist working in Pain, gives good background detail on acute and chronic pain and its impact.  Though it is written for professionals, the terminology is very comprehensible and we hope you may find it useful.


A very well produced video from Australia gives an excellent five-minute overview of chronic pain and some of its issues.  Two other excellent explanatory videos can be accessed here and here.






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Pain Service Website, Gloucestershire Hospitals NHS Foundation Trust
Webmaster Dr J G de Courcy, Consultant in Pain Medicine and Anaesthesia
email: pain.webmaster[at]

Page updated 22/6/2016