fever

Fever is a higher-than-normal body temperature.

 

Normal temperature is usually defined as 98.6 degrees Fahrenheit (F) or 37 degrees Celsius (C), though body temperature varies normally by a few tenths of a degree depending on the individual, on how the temperature is measured, and what time of day it is.

 

Most healthcare professionals would say a person truly has a fever when the temperature is greater than 99.5 degrees F or 37.5 degrees C when measured orally, or 100.4 degrees F or 38 degrees C when measured rectally.

 

Normal body temperature changes during the day. Exercise, stress, or dehydration may cause a person's temperature to go up temporarily. If temperature returns to normal when the person is rested and hydrated, there is usually no reason to look for other causes.

 

Fever is a symptom, not a disease. A fever may mean that there is something else going on in the body that is causing it. A higher body temperature gives the immune system an advantage in fighting bacteria and viruses because most of them do not survive well at higher temperatures.

 

The signs and symptoms of a fever depend on what is causing it. At first, a fever can cause a chill. When the brain raises the body's "thermostat," the body responds by shivering to raise the temperature. Shivering produces heat in the body. Once the temperature goes up, the person often feels warm. When the brain then lowers the thermostat, the person may start to sweat to bring the temperature down.

 

Fever can be caused by almost any infectious condition. Some of the more common in otherwise healthy individuals in the U.S. include strep throat caused by group A strep, pneumonia caused by Mycoplasma or Streptococcus pneumoniae, influenza ("the flu"), chickenpox, the common cold, ear infections in children, or urinary tract infections in adult women. In parts of Asia and Africa, malaria is the first thing to suspect if a person has a high fever.

Generally, nothing should be done to prevent fevers because they are an important signal to what might be wrong with the body. Some causes can be prevented, for example, a person should avoid staying in a hot environment for too long. It is very important to drink more fluids than usual after heavy exercise, especially when it is hot outside.

A thermometer is used to measure the temperature. The temperature can be taken in the mouth, rectum, or ear. When measured in the rectum, the temperature is about a half degree C higher than in the mouth. If necessary, the temperature can also be measured under the arm or on the skin, though readings at these sites are less accurate.