Pyrexia is a fairly common word to find on the back of many medications you might use every day. However despite this, many people don’t actually know what it means, or what its implications might be. Pyrexia actually comes from the ancient Greek word pyretos meaning fire, and from the Latin word febris, meaning fever.
Most medical texts describe fever as when the body temperature is raised above 38 degrees centigrade, or 100.8 Fahrenheit. This can sometimes be deceptive however, as our body temperature can rise and fall naturally at certain times of the day anyway. Also when women are menstrating their body temperature will often be raised slightly as well, which can sometimes give the impression fever is present.
The occurrence of pyrexia is controlled by the hypothalamus, which in turn relays messages to the rest of the body. Therefore if an infection or dangerous element is detected, the hypothalamus sends messages reporting that the body feels cold to the relevant areas. This is why the muscles will become more active and why shivering takes place. This is also the reason that you will often feel as if you are cold when you have a fever and are in fact very hot.
If the body becomes too hot then hyperpyrexia can often set in. This is when the body temperature becomes dangerously high, although differs from hyperthermia. Hyperthermia being when the temperature is raised above the body’s set level, and hyperpyrexia being where the body sets the standard body temperature too high. This condition is very often fatal, and can cause a wide range of different complications. Fortunately enough however it is not that common in very severe cases.
Although pyrexia is actually used to describe fever, it is often confused with either Hyperthermia or Hypothermia. Hyperthermia is a basically an extreme form of fever where the increase in body temperature is to such an extent as to cause permanent or life threatening damage. By contrast Hypothermia is when the body temperature has been lowered to the point that damage may occur. So although often confused because of the similar names they are in fact the complete opposites of each other.
Fever is actually one of the body’s defense mechanisms rather than a symptom of any particular disease in itself. The reason being that most viruses and bacteria can only reproduce under certain circumstances. The reproduction and increasing numbers of these cells is what makes us more or less ill. So the more an infection can spread the worse it will become. However making the temperature of the body too hot for it to reproduce can effectively stop the infection. While the infection is stopped from reproducing, this gives the body’s natural antibodies more time to kill the remaining infectious and harmful cells.
As well as hindering the progression of certain ailments, there are some antibodies and processes in the body’s defense which are increased due to a higher temperature being encountered. In this way the body can usually gain a boost and end an infection sooner than if the fever were not encountered. For example white blood cells are produced much faster when the body temperature is raised above the normal level. Also the detrimental effects of endotoxins is lessened.
On the negative side of having a fever however, prolonged higher temperatures of the body can result in weight loss and can put a strain on the vital organs. Furthermore fever leaves a person with very little energy as all the bodies energy is burned up by the higher functioning of the bodily processes. These include shivering, increased heart and perspiration rates as well as blood vessel dilation. Furthermore if a fever lasts too long, then exhaustion can set in, which in turn inhibits the body’s natural responses to invading particles and infections.
Because of there being negative and positive sides to the se of fever in the recovery process, there are some who believe that it should and should not be encouraged. The evidence generally shows however that either extreme is detrimental and that the use of controlled fever under some circumstances is the best approach to use.