A fever, or uptick in a person’s internal thermostat, is one of the ways the body fights off infection and illness. Researchers believe that this warming may help destroy bacteria and viruses that are sensitive to temperature changes. Most of the time, fevers go away on their own within a few days.

The hypothalamus, a section of the brain located in the middle of the brain’s base, controls the body’s temperature. It’s normally set at around 98.6°F, although it tends to be a degree lower in the morning and higher in the afternoon. But when viruses or bacteria invade the body, the hypothalamus resets the baseline at a higher number, such as 102°F. As a result, you may experience sweating, chills, muscle aches, and a loss of appetite as the body attempts to cool itself. The old wives’ tale stating “feed a cold, starve a fever” is untrue. The body requires calories to fight off an infection; experts recommend trying to keep up normal food intake and replenishing fluid levels by drinking plenty of liquids. A sunburn or heat exhaustion may also trigger a fever.

Although they make us feel miserable, fevers aren’t usually dangerous in adolescents unless they’re higher than 103°F. In young children and infants, however, even a mild fever may indicate a serious infection; you should call a physician if a baby or young child has one. To check for a fever, you can use a thermometer inserted into the mouth, armpit, or rectum. (Armpit, forehead, and mouth readings are typically about 1 degree lower than a temperature taken in the rectum.) Ask your doctor for advice about when to call and what to do.

Drinking plenty of fluids and taking a lukewarm sponge bath may provide some relief from a fever. Although a cold bath may seem tempting, by lowering the skin temperature, it can actually cause a fever to rise. To help lower a fever, acetaminophen or ibuprofen is often effective. But avoid giving aspirin to children, as it can cause Reye’s syndrome, a rare but serious condition.

ADDITIONAL FACTS

  1. The Italian astronomer and physicist Galileo (1564–1642) invented a water thermometer in 1593. In 1714, Daniel Gabriel Fahrenheit (1686–1736) made the first mercury thermometer.
  2. A much-lower-than-normal temperature may indicate neurological impairment, severe bacterial infection, or a suppressed immune system.