Fever's role in infections

Fever's role in infections

What a fever means

A fever in infants and children can be scary, but it is common. It means your child's body is most likely reacting to an infection.

Your child has a fever if her temperature is higher than 100.4 degrees F by rectum. A rectal temperature is most accurate for children younger than 2 years old.

The degree of fever does not always show how bad an illness may be. Children often run a higher temperature than adults for the same illness.

More important than the fever is how your child looks and acts. Watch your child for signs of illness that include:

  • appetite loss, abdominal pain or both
  • headache
  • weakness, fatigue or both
  • thirst
  • dry skin
  • sore throat or swallowing problems
  • breathing problems
  • ear pain
  • You should talk with your health care provider before giving fever-reducing medicine to a child younger than 2 months old.
  • Use a rectal thermometer to get an accurate temperature reading for newborns to 1 year olds. Follow the package directions.
  • Don't give your child hot or cold liquids before taking his temperature by mouth.

When you should call your health care provider

Call your health care provider for an appointment if:

  • your child is younger than 2 months old and has a temperature of at least 100.4 F by rectum
  • your child is 2 to 3 months old and has a temperature of more than 101 F by rectum and has signs of illness
  • your child has a temperature higher than 104 F by rectum
  • your child's fever does not go down within 24 hours
  • you gave your child over-the-counter fever medicine but the fever and signs of illness last for three days
  • your child breaks out in a rash
  • your child vomits

If you think your child is ill and you aren't comfortable with the way she looks or behaves, call your health care provider for an exam as soon as possible, especially if your child has a fever and is unusually irritable, appears ill, has a stiff neck or has problems breathing.

How to take your child's temperature

  • After each use, wash the thermometer in clean, warm, soapy water. Wipe it with rubbing alcohol.
  • Clear the thermometer of the previous reading by following the package directions.
  • Be with your child to make sure she stays still.

If you have a mercury thermometer, take it to a household hazardous waste collection facility. Do not use it and do not throw it in the garbage.

There are five ways you can take a temperature. Tell your health care provider knows which way you used.


  • Coat the tip of the rectal thermometer with a lubricant (such as Vaseline® or KY Jelly®).
  • Gently insert the thermometer into your child's rectum. Do not go farther than the end of the silver tip, which is about 1/4 inch.
  • Hold the thermometer in place for two to three minutes or until a digital thermometer beeps (usually 10 seconds).

Armpit (axillary)

  • You may use a digital thermometer.
  • Make sure your child's armpit is dry.
  • Put the bulb under your child's arm, snug against her body.
  • Make sure the thermometer stays in place for three to four minutes or until a digital thermometer beeps (usually 10 seconds).

Mouth (oral)

  • Only use this method if your child understands that she must not bite the thermometer. This is usually around age 3.
  • You may use a glass or digital thermometer.
  • Put the bulb end of the thermometer under your child's tongue. Tell her to close her mouth but not to bite the thermometer.
  • Keep it in place for two minutes or until a digital thermometer beeps (usually 10 seconds).


  • Do not use on an infant younger than 6 months old.
  • Follow the ear probe package directions carefully.


  • Use as directed.

Source: Allina Health's Patient Education Department, Guide for the Care of Children: Ages Birth to 5 Years Old, fifth edition. For inclusivity, this guide uses "them" and "their."
Reviewed By: Allina Health's Patient Education Department experts, including the Pediatric Department of Allina Health Coon Rapids Clinic
First Published: 02/01/2010
Last Reviewed: 01/01/2016