A “fever” is a core temperature of 100.4° F or higher in an infant from birth through age 3 months and a core temperature of 101° F or higher in any child over 3 months of age. Core temperatures can be taken rectally (in young children), orally (children 5 years and up who can hold a thermometer under the tongue without biting it for 2 minutes), or in the ear of children 5 years and up with the appropriate device. While underarm temperatures can give you a clue as to whether or not your child has a fever, they are unreliable. If your child has an underarm temperature of 99° F or higher, you should take a core temperature.

While many parents may feel reluctant to take rectal temperatures on their children, it is a relatively simple procedure with low risks when performed correctly. Information on the technique and supplies required can be found in most books on childcare and rearing.

If your child has a fever, it is probably a sign that his/her body is fighting an infection. When your child becomes ill because of a virus or bacteria, his/her body may respond by increasing body temperature. It is important to remember that, except in the case of heat stroke, fever itself is not an illness only a symptom of one. Fever itself also is not a sign that your child needs an antibiotic.

Many conditions, such as an ear infection, a common cold, the flu, a urinary tract infection or pneumonia, may cause a child to develop a fever. In some cases, medication, injury, poison or an extreme level of over activity may produce a fever. An environment that is too hot may result in heat stroke, a potentially dangerous rise in body temperature. It is important to look for the cause of the fever in infants because the cause of newborn fevers can be life threatening. In older children, it is important to look for a cause of fever when the child is irritable.

Fevers are generally harmless and help your child fight infection. They can be considered a good sign that your child’s immune system is working and the body is trying to rid itself of the infection.

If your child has a fever, his/her heart and breathing rates will naturally speed up. You may notice that your child feels warm. He/She may appear flushed or perspire more than usual. His/Her body also will require more fluids. Some children feel fine when they have a fever. However, most will have symptoms of the illness that is causing the fever. Your child may have an earache, a sore throat, a rash or a stomachache. These signs can provide important clues as to the cause of your child’s fever.

Most fevers less than 101° F may be treated safely at home with acetaminophen (Tylenol) or ibuprofen (Motrin) however, you should call your pediatrician if:

  • Your child is less than 2 months old and has a rectal temperature of 100.4° F or higher.
  • Your child is older than 2 months old and has a temperature of 101° F or higher.
  • Your child has a fever and is acting like he/she is in pain.
  • The fever lasts more than 72 hours.
  • You feel your child is getting worse.

The response or lack of response of fever to medicines tells us little about the severity of the infection. If your child smiles, plays, and drinks adequate fluids, you need not worry about the fever or what is causing the fever. It is likely caused by a benign viral illness.

Tylenol and Motrin Dosing Information (PDF)