Fever

Fever is a rise in body temperature caused by the body's response to illness.

Normal human body temperature changes during each 24-hour period according to a definite pattern. It is lowest in the morning before dawn and highest in the afternoon. Temperature control actions in the body keep the amount of heat that is made equal to the amount lost. This keeps body temperature normal.

An abnormal rise in body temperature is caused by either a condition called hyperthermia or fever. Hyperthermia is caused by a breakdown in the body's temperature control actions. In fever, the temperature controls in the body are working as they should, but body temperature rises as the body responds to illness.

There are three phases of fever:

Certain problems are more likely in older people or the very young. In older people, the temperature control centers in the brain may not work the way they should and can lead to hyperthermia. This may cause irregular heartbeat, lack of blood flow to parts of the body, confusion, or heart failure. In children between 6 months and 6 years old, high fever may lead to seizures.

To read the rest of this article from the National Cancer Institute, click here.

a hand holding an old fashioned mercury thermometer

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