Fever, Age 3 and Younger

Topic Overview

Fever is the body's normal and healthy reaction to infection and other illnesses, both minor and serious. Fevers help the body fight infection. Fever is a symptom, not a disease. In most cases, fever means your child has a minor illness. Often you must look at your child's other symptoms to determine how serious the illness is. Although it may be scary when your child's temperature goes up, fever is not harmful.

Normal body temperature

The average normal body temperature is about 37°C (98.6°F). It usually rises during the day from a low of 36.5°C (97.7°F) in the morning to a high of 37.5°C (99.5°F) in the late afternoon. Each child has a normal temperature range that may be different from another child's. Mild increases to 38°C (100.4°F) can be caused by exercising, wearing too many clothes, taking a hot bath, or being outside in hot weather.

Fever

A child has a fever when his or her temperature is 37.4°C (99.3°F) or higher, measured in the armpit (axillary). An axillary temperature is a common method for checking a fever in a young child. Axillary temperatures read from 0.3° C to 0.6° C lower than oral temperatures. All temperature guidelines listed in this topic are axillary. Other ways to measure temperature, such as ear probe thermometers, forehead temperature strips, or pacifier thermometers, may also be used. For information about taking accurate temperatures, see the topic Body Temperature.

If you think your child has a fever but you are not able to measure his or her temperature, it is important to look for other symptoms of illness.

Children tend to run higher fevers than adults. The degree of fever may not indicate how serious your child's illness is. With a minor illness, such as a cold, a child may have a temperature of 40°C (104°F); a very serious infection may not cause a fever or may cause only a mild fever. It is important to look for other symptoms along with the fever.

A fever in a healthy child is usually not dangerous, especially if the child does not have other symptoms and the fever goes away in 3 to 4 days. Most children who have a fever will be fussy and play less and may not eat as much as usual.

High fevers may make your child uncomfortable, but they rarely cause serious problems. There is no medical evidence that fevers from infection cause brain damage. The body limits a fever caused by infection from rising above 41°C (106°F). However, outside heat—such as from being in a car that is parked in the sun—can cause body temperature to rise above 41.5°C (106.7°F), and brain damage can occur.

Childhood immunizations can reduce the risk for fever-related illnesses, such as Haemophilus influenzae type b (Hib) infection. Although no vaccine is 100% effective, most routine childhood immunizations are effective for 85% to 95% of the children who receive them. For more information, see the topic Immunizations.

Causes of fever

It is not unusual for a preschool-aged child to have 7 to 10 viral infections in a year. Each new viral infection may cause a fever. It may seem that a fever is ongoing, but if 48 hours pass between fevers, then the new fever is most likely from a new illness.

Common causes of fever include:

• Viral infections, such as colds, flu, and chicken pox.
• Bacterial infections, such as a urinary tract infection.
• Immunizations.

Teething does not cause a fever. If a baby is teething and has a fever, look for other symptoms that may need to be evaluated.

A fever that increases quickly may lead to a fever seizure in some children. If your child has a high fever and a seizure, see the topic Fever Seizures.

Review the Emergencies and Check Your Symptoms sections to determine if and when you need to see a health professional.

	Go to top of page	Go to next section
Author:	Jan Nissl, RN, BS	Last Updated: June 22, 2007
Medical Review:	Michael J. Sexton, MD - Pediatrics Thomas Emmett Francoeur, MDCM, CSPQ, FRCPC - Pediatrics
© 1995-2008 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.This information does not replace the advice of a doctor. Healthwise disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. How this information was developed to help you make better health decisions.