Fever in Children


The definition of fever in a child depends on the child's age and general health.

For infants younger than 3 months of age and for all children with an abnormal immune system, a fever is defined as a temperature of 100.4 degrees Fahrenheit (38 degrees Celsius) and higher. The temperature should be measured rectally for very young infants, but other methods (orally, under the arm) of measuring fever may be required for children with problems of the immune system.

For older infants and children and those without a problem of the immune system, most doctors define fever as a temperature of 101.2 degrees Fahrenheit (38.4 degrees Celsius) and higher when taken by any method (orally, rectally, under the arm, etc.).

The body has several ways to maintain normal body temperature. The organs involved in helping with temperature regulation include the brain, skin, muscle, and blood vessels. The body responds to changes in temperature by:

  • Increasing or decreasing sweat production.
  • Moving blood away from, or closer to, the surface of the skin.
  • Getting rid of, or holding on to, water in the body.
  • Seeking a cooler or warmer environment.

When your child has a fever, the body works the same way to control the temperature, but it has temporarily reset its thermostat at a higher temperature. The temperature increases for a number of reasons:

  • Chemicals, called cytokines and mediators, are produced in the body in response to an invasion from a microorganism, malignancy, or other intruder.
  • The body is making more macrophages, which are cells that go to combat when intruders are present in the body. These cells actually "eat-up" the invading organism.
  • The body is busily trying to produce natural antibodies, which fight infection. These antibodies will recognize the infection next time it tries to invade.
  • Many bacteria are enclosed in an overcoat-like membrane. When this membrane is disrupted or broken, the contents that escape can be toxic to the body and stimulate the brain to raise the temperature.

Patients can be seen by Texas Children's experts in Infectious Disease.

Causes & Risk Factors

The following conditions can cause a fever:

  • Infectious diseases
  • Certain medications
  • Heat stroke
  • Blood transfusion
  • Disorders in the brain
  • Some kinds of cancer
  • Some autoimmune diseases

What are the benefits of a fever?

Fever is not an illness. It is a symptom, or sign that your body is fighting an illness or infection. Fever stimulates the body's defenses, sending white blood cells and other "fighter" cells to fight and destroy the cause of the infection.

Symptoms & Types

Children with fevers may become more uncomfortable as the temperature rises. The following are the most common symptoms of a fever. However, each child may experience symptoms differently. In addition to an elevated body temperature, symptoms may include:

  • Your child may not be as active or talkative as usual.
  • He may seem fussier, less hungry, and thirstier.
  • Your child may feel warm or hot. Remember that even if your child feels like he is "burning up," the measured temperature may not be that high.

The symptoms of a fever may resemble other medical conditions. According to the American Academy of Pediatrics, if your child is younger than 3 months of age and has a temperature of 100.4 degrees Fahrenheit (38 degrees Celsius) or higher, you should call your child's health care provider immediately. If you are unsure, always check with your child's health care provider for a diagnosis.

When should a fever be treated?

In children, a fever that is making them uncomfortable should be treated. Treating your child's fever will not help the body get rid of an  infection or illness any faster; it simply will relieve discomfort associated with fever. Children between the ages of 6 months and 5 years can develop seizures from fever (called febrile seizures). If your child does have a febrile seizure, there is a chance that the seizure may occur again, but, usually, children outgrow the febrile seizures. A febrile seizure does not mean your child has epilepsy. There is no evidence that treating the fever will reduce the risk of having a febrile seizure.

What can I do to decrease my child's fever?

Specific treatment for a fever will be determined by your child's health care provider based on:

  • Your child's age, overall health, and medical history
  • How sick he is
  • Your child's tolerance for specific medications, procedures, or therapies
  • How long the illness is expected to last
  • Your opinion or preference

To relieve a fever, administer an anti-fever medication, such as acetaminophen or ibuprofen. DO NOT give your child aspirin, as it has been linked to a serious, potentially fatal disease, called Reye syndrome.

Other ways to reduce a fever:

  • Dress your child lightly. Excess clothing will trap body heat and cause the temperature to rise.
  • Encourage your child to drink plenty of fluids, such as water, juices, soda, punch, or popsicles.
  • Give your child a lukewarm bath. Do not allow your child to shiver from cold water, as this can raise the body temperature. NEVER leave your child unattended in the bathtub. 
  • DO NOT use alcohol baths.

When should I call my child's health care provider?

Call your child's health care provider immediately if your child is younger than 3 months old and his or her temperature is 100.4 degrees Fahrenheit (38 degrees Celsius) or higher.

If your child is older than 3 months, call your child's provider right away if:

  • Your child is crying inconsolably.
  • Your child is difficult to awaken.
  • Your child has been in a very hot place, such as inside a hot car. 
  • Your child has a seizure (convulsion).
  • Your child has other symptoms such as a severe headache, stiff neck, or an unexplained rash. 
  • Your child is taking steroids or has an immune system problem, such as cancer. 
  • Your child looks or acts very sick.
  • The fever rises repeatedly to 104 degrees Fahrenheit (40 degrees Celsius) or higher. 
  • Your child has severe vomiting or diarrhea. 

Call your child's provider during office hours if any of the following conditions are present:

  • Your child is 2 years or younger, and the fever persists for more than 24 hours. 
  • Your child is older than 2 years and has had a fever more than 72 hours.
  • Your child seems to be getting worse or still acts sick when the fever comes down. 
  • You have other concerns or questions.