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 their temperature is higher than 100.4 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 (tiredness) 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 instructions.
  • Don't give your child hot or cold liquids before taking their 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 your child appears ill and you are not comfortable with the way they look, call your health care provider right away, especially if your child has a fever (higher than 101.5 F), is unusually irritable, is not drinking enough liquids and has a lack of urine, has a stiff neck or is having trouble breathing. Same day appointments are available or you will be given other instructions for other medical care.

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 instructions.
  • Be with your child to make sure they stay 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 their 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 they 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 them to close their 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.

Temporal (forehead)

  • Use as directed.

Source: Allina Health's Patient Education, Guide for the Care of Children: Ages Birth to 5, sixth edition, ped-ah-91554
First Published: 02/01/2010
Last Reviewed: 11/16/2022