Fever

Fever, also known as pyrexia, or a febrile response, is a medical symptom which describes an increase in internal body temperature to levels which are above normal (37 degrees Celsius, 98.6 degrees Fahrenheit). Fever should not be confused with Hyperthermia, which is an increase in body temperature over the body?s thermoregulatory set-point (approximately 37 degrees Celsius). A fever is most accurately characterized as a temporary elevation in the body?s thermoregulatory set-point, which is usually by about 1-2 degrees Celsius. This elevation in thermoregulatory set-point means that the previous "normal body temperature" would be considered hypothermic. Effector mechanisms, such as increased blood pressure, increased heart rate, activation of brown adipose tissue and muscular shivering attempt to counteract the perceived hypothermia, thereby reaching the new thermoregulatory set-point.

Types

Pyrexia can be classed as low grade (38 to 39 °C, 100 to 102.2 °F), moderate (39 to 40 °C, 102.2 to 104 °F), or high grade (more than 40 °C or 104 °F) depending on how much the body temperature has deviated from normal.

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Fever may be of benefit and is part of the body's response to a disease; however, if the fever goes above 42 °C (107.6 °F) then it may cause significant tissue damage and would most certainly be harmful. This is termed hyperpyrexia. 43.3oC (110oF) is considered the upper limit compatible with life.

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Temperature normally fluctuates over the day, and the same applies to fever. If this characteristic pattern is lost, the raised body temperature may be due to hyperthermia, a more dangerous disorder. Hyperthermia is commonly caused by overheating or sunstroke, which elevates the body's temperature above the thermoregulatory set-point.

Related Topics:
Hyperthermia - Sunstroke

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