Patient information: Fever in children

FEVER OVERVIEW

Fever is a normal response to a variety of conditions, the most common of which is infection. Fever occurs when the body's temperature is elevated as a result of the body's thermostat being reset to a higher than usual temperature.

Nearly every child will develop a fever at some point. The challenge for parents is to know when to be concerned. This topic review will discuss the definition of a fever, how to accurately measure a child's temperature, how and when to treat fever, and signs and symptoms that require further evaluation.

TEMPERATURE CONTROL

The body's temperature is controlled by a part of the brain (the hypothalamus). Body temperature varies over the course of the day, although the hypothalamus usually is able to maintain it within a relatively narrow range. The hypothalamus regulates temperature by balancing heat production in the muscles and the liver with heat loss from the skin and lungs.

Fever occurs when the hypothalamus increases the body's temperature. This may be in response to the immune system detecting an infectious agent, such as a bacterium or virus.

FEVER DEFINITION

Because of the normal variation in body temperature, there is no single value that is defined as fever. However, the following are generally accepted values:

• Rectal temperature above 100.4ºF (38ºC)
• Oral temperature above 99.5ºF (37.5ºC)
• Axillary (armpit) temperature above 99ºF (37.2ºC)
• Digital pacifier temperature above 100ºF (37.8ºC)
• Ear temperature above 100.4º (38ºC) in rectal mode or 99.5ºF (37.5ºC) in oral mode

FEVER CAUSES

Infection is the most common cause of fever in children. Common viral and bacterial illnesses like colds, gastroenteritis, ear infections, croup, and bronchiolitis are the most likely illnesses to cause fever. (See "Patient information: Croup in infants and children" and "Patient information: Bronchiolitis in infants and children" and "Patient information: Urinary tract infections in children".)

Teething probably does not cause fever. In particular, studies have shown that temperatures of 101.3ºF (38.5ºC) or greater are unlikely to be related to teething.

Bundling a child who is less than three months old in too many clothes or blankets can increase the child's temperature slightly. However, a rectal temperature of 101ºF (38.5ºC) or greater is not likely to be related to bundling and should be evaluated (see 'Evaluation recommended' below.

Some childhood immunizations can cause fever. The timing of the fever varies, depending upon which vaccination was given. (See "Patient information: Immunizations for infants and children age 0 to 6 years".)

HOW DO I MEASURE MY CHILD'S TEMPERATURE?

The best way to measure a child's temperature depends upon several factors. In all children, a rectal temperature is the most accurate. However, it is possible to accurately measure the temperature in the mouth (for children older than four or five years) or ear (for children older than six months) when the proper technique is used.

Temperatures measured in the armpit are the least accurate, but may be useful as a first test in an infant who is younger than three months. If the armpit temperature is over 99ºF (37.2ºC), the rectal temperature should be measured.

It is not accurate to measure a child's temperature by feeling the child's skin. This is called a tactile temperature, and it is highly dependent upon the temperature of the person who is feeling the child's skin.

Glass versus digital thermometers — Digital thermometers are inexpensive, widely available, and are the most accurate way to measure temperature. A variety of styles are available.

Glass thermometers that contain mercury are not recommended due to the potential risks of exposure to mercury (which is toxic) if the thermometer is broken. If a digital thermometer is not available, be sure to carefully "shake down" the glass thermometer before use. Instructions for disposing of thermometers that contain mercury are available online (www.epa.gov/mercury/spills/index.htm).

Other types of thermometers are available, including plastic strip, forehead, and pacifier thermometers. However, these are not as accurate as digital thermometers and are not recommended.

Rectal temperature

• The child or infant should lie down on their stomach across an adult's lap.
• Apply a small amount of petroleum jelly (eg, Vaseline) to the end of the thermometer.
• Gently insert the thermometer into the child's anus until the silver tip of the thermometer is not visible (1/4 to 1/2 inch inside the anus, (figure 1).
• Hold the thermometer in place. A glass thermometer requires 2 minutes while most digital thermometers need less than one minute.

Oral temperature — Do not measure the temperature in a child's mouth if he or she has consumed a hot or cold food or drink in the last 30 minutes.

• Clean the thermometer with cool water and soap. Rinse with water.
• Place the tip of the thermometer under the child's tongue towards the back. Ask the child to hold the thermometer with his or her lips.
• Keep the lips sealed around the thermometer. A glass thermometer requires about 3 minutes while most digital thermometers need less than one minute.

Armpit temperature

• Place the tip of the thermometer in the child's dry armpit.
• Hold the thermometer in place by holding the child's elbow against the chest for 4 to 5 minutes.

Ear temperature — Ear thermometers are not reliable in infants less than 6 months old. If the child has been outside on a cold day, wait 15 minutes before measuring the ear temperature. Ear tubes and ear infections do not affect the accuracy of an ear temperature.

• To measure temperature accurately in the ear, the parent must pull the child's outer ear backwards before inserting the thermometer (figure 2).
• Hold the ear probe in the child's ear for about two seconds.

SHOULD I TREAT MY CHILD'S FEVER?

There are pros and cons of treating fever. Fever may play a role in fighting infection, although it can make a child uncomfortable.

The height of a child's fever is not always the best indicator of whether the child needs to be treated and/or evaluated. Instead, it is important to note how a child behaves and appears. Fever is usually accompanied by other symptoms. Some of these symptoms require evaluation by a health care provider, even if there is no fever. The table provides a list of these symptoms (table 1).

In most cases, a child with a fever can be observed and/or treated at home. However, it is important for parents to know when a child with a fever needs to be evaluated by a healthcare provider, when fever should be treated, and when it is reasonable to observe the child without treating the fever.

These are general guidelines that do not necessarily apply to every situation; parents who have questions or are concerned about their child should contact their child's healthcare provider for advice.

Evaluation recommended — A healthcare provider should be consulted in the following situations:

• Infants who are less than three months of age who have a temperature of 100.4ºF (38ºC) or greater, regardless of how the infant appears (eg, even well-appearing young infants should be evaluated)
• Children who are older than three months who have a temperature of 100.4ºF (38ºC) or greater for more than three days or who appear ill (eg, fussy, clingy, refusing to drink fluids)
• Children who are three to 36 months who have a temperature of 102ºF (38.9ºC) or greater
• Children of any age whose temperature is 104ºF (40ºC) or greater
• Children of any age who have a febrile seizure. Febrile seizures are convulsions that occur when a child (between six months and six years of age) has a temperature greater than 100.4º F (38º C). (See "Patient information: Febrile seizures".)

• Children of any age who have recurrent fevers, even if the fevers only last a few hours
• Children of any age who have a fever and have a chronic medical problem such as heart disease, cancer, lupus, or sickle cell anemia
• Children who have a fever as well as a new skin rash

Treatment recommended — Treatment of fever is recommended if a child has an underlying medical problem, including diseases of the heart, lung, brain, or nervous system, or if the child has had febrile seizures in the past.

Treatment is helpful if the child is uncomfortable, although it is not necessary.

Treatment not required — In some cases, it is not necessary to treat a child's fever. A child older than three months who has a temperature less than 102ºF (38.9ºC), who is otherwise healthy and acting normally, does not require treatment. However, parents who are unsure if their child's fever needs treatment should contact the child's healthcare provider. (See 'Evaluation recommended' above.)

FEVER TREATMENT OPTIONS

Medications — The most effective way to treat fever is to use a medication such as acetaminophen (eg, Tylenol®) or ibuprofen (Advil®, Motrin®). These treatments can reduce the child's discomfort and lower the child's temperature by 2 to 3ºF (1 to 1.5º C). Aspirin is not recommended for children under age 18 years due to concerns that it can cause a rare but serious illness known as Reye syndrome.

Acetaminophen may be given every four to six hours as needed. If the temperature remains elevated despite acetaminophen and the child is greater than 6 months of age, ibuprofen may be given every six hours in place of acetaminophen. The dose of acetaminophen or ibuprofen should be calculated based upon the child's weight (not age). The tables provide the recommended dose of acetaminophen and ibuprofen by weight (table 2 and table 3).

There are inadequate data regarding the safety of giving alternating doses of acetaminophen and ibuprofen. Although this is commonly recommended, parents should understand that giving combinations of acetaminophen and ibuprofen may not be as safe as using one drug alone.

Fever-reducing medications should only be given as needed, and discontinued once bothersome symptoms have resolved.

Sponging and baths — Sponging involves placing a child in a bathtub and using a damp washcloth to apply comfortably warm (85ºF or 30ºC) water to the entire body. Cooling occurs as water evaporates from the skin surface. Therefore, the child should not be wrapped in wet towels or submerged in water when this method of cooling is used.

Sponging is rarely necessary to treat fever because it is not as effective as anti-fever medications such as acetaminophen. If sponging is used, it should always be used in conjunction with anti-fever medications, such as acetaminophen, unless the child cannot tolerate these medications.

Sponging with alcohol is never recommended because alcohol fumes may be absorbed through the child's skin or lungs.

Increase fluids — Having fever can increase a child's risk of becoming dehydrated. To reduce this risk, parents should encourage their child to drink an adequate amount of fluids. Children with fever may not feel hungry and it is not necessary to force them to eat. However, fluids such as milk (cow's or breast), formula, and water should be offered frequently. Older children may eat flavored gelatin, soup, or frozen popsicles. If the child is unwilling or unable to drink fluids for more than a few hours, the parent should consult the child's healthcare provider.

Rest — Having a fever causes most children to feel tired and achy. During this time, parents should encourage their child to rest as much as the child wants. It is not necessary to force the child to sleep or rest if he or she begins to feel better. Children may return to school or other activities when the temperature has been normal for 24 hours.

WHERE TO GET MORE INFORMATION

Your child's healthcare provider is the best source of information for questions and concerns related to your child's medical problem. Because no two people are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your child's situation.

This discussion will be updated as needed every four months on our web site (www.uptodate.com/patients). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.

Some of the most pertinent include:

Patient Level Information:
Patient information: Croup in infants and children
Patient information: Bronchiolitis in infants and children
Patient information: Urinary tract infections in children
Patient information: Immunizations for infants and children age 0 to 6 years
Patient information: Febrile seizures

Professional Level Information:
Approach to the child with fever of unknown origin
Definition and etiology of fever in neonates and infants (less than three months of age)
Drug fever
Etiologies of fever of unknown origin in children
Evaluation and management of fever in the neonate and young infant (less than three months of age)
Fever without a source in children 3 to 36 months of age
Pathophysiology and treatment of fever in infants and children
Strategies for the evaluation of fever in neonates and infants (less than three months of age)

A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable.

• National Library of Medicine

      (www.nlm.nih.gov/medlineplus/healthtopics.html)

• American Academy of Pediatrics

      (www.aap.org/healthtopics/commonillness.cfm)

• The Nemours Foundation

      (www.kidshealth.org/parent/general/body/fever.html, available in Spanish)

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