Patient education: Fever in children (Beyond the Basics)

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 caregivers 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.

FEVER DEFINITION — Because of the normal variation in body temperature, there is no single value that is defined as fever. In general, a fever means a temperature above 100.4°F (38°C). You might get slightly different numbers depending on how you take your child's temperature – oral (mouth), axillary (armpit), ear, forehead, or rectal.

Axillary, ear, and forehead temperature measurements are easier to obtain than rectal or oral temperatures, but they are less accurate and may need to be confirmed rectally or orally in certain children.

FEVER CAUSES — Infection is the most common cause of fever in children. Common viral and bacterial illnesses are the most likely illnesses to cause fever. These include:

●Colds (see "Patient education: The common cold in children (Beyond the Basics)")

●Gastroenteritis (see "Patient education: Nausea and vomiting in infants and children (Beyond the Basics)")

●Ear infections (see "Patient education: Ear infections (otitis media) in children (Beyond the Basics)")

●Croup (see "Patient education: Croup in infants and children (Beyond the Basics)")

●Bronchiolitis (see "Patient education: Bronchiolitis and RSV in infants and children (Beyond the Basics)")

●Urinary tract infections (see "Patient education: Urinary tract infections in children (Beyond the Basics)")

There is little or no scientific evidence to support the widespread belief that teething causes fever. Although it is difficult to disprove this notion completely, alternative causes of fever should always be sought and temperatures above 102°F (38.9°C) should never be attributed 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 101°F (38.5°C) 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 education: Vaccines for infants and children age 0 to 6 years (Beyond the Basics)".)

HOW DO I MEASURE MY CHILD'S TEMPERATURE?

Glass versus digital thermometers — Digital thermometers are inexpensive, widely available, and 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).

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

Where to measure temperature — The best way to measure a child's temperature depends upon several factors. For children who can hold a thermometer under the tongue using proper technique (usually children older than four or five years), temperature can be measured accurately in the mouth. For infants and children who cannot hold the thermometer under the tongue, temperature can be measured in the armpit. If the armpit temperature is over 99°F (37.2°C) and there is concern that the child is ill, a rectal temperature may be necessary. A rectal temperature is also appropriate for infants from birth to three months of age. In the hospital setting, a rectal temperature is usually obtained before making medical decisions (eg, whether to obtain laboratory tests).

Temperatures measured in the ear or on the forehead also are less accurate than temperatures measured rectally or orally and may need to be confirmed by one of these methods.

It is not accurate to estimate 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.

How to measure temperature at specific sites

●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 two minutes, while most digital thermometers need less than one minute.

●Oral temperature – Do not measure the temperature in a child's mouth if they have 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 toward the back. Ask the child to hold the thermometer with their lips.

•Keep the lips sealed around the thermometer. A glass thermometer requires approximately three 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 four to five minutes.

●Ear temperature – Ear thermometers are not as accurate as rectal or oral thermometers. 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 caregiver must pull the child's outer ear backward before inserting the thermometer (figure 2).

•Hold the ear probe in the child's ear for approximately two seconds.

●Temporal artery temperature – The temperature of the temporal artery can be taken by a device that is run over the forehead and in front of the ear (contact) or one that takes the temperature without touching your child using an infrared sensor (noncontact). These devices are not as accurate as a rectal or oral temperature but may be used to screen for fever in children older than four years of age.

SHOULD I TREAT MY CHILD'S FEVER? — There are pros and cons of treating fever. Fever may play a role in fighting infection, but it can also 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 some 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 caregivers to know when a child with a fever needs to be evaluated by a health care provider, when fever should be treated, and when it is reasonable to observe the child without treating the fever.

The guidelines provided below are general guidelines that do not apply to every situation; caregivers who have questions or are concerned about their child should contact their child's health care provider for advice.

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

●Infants who are less than three months of age who have a rectal temperature of 100.4°F (38°C) or greater, regardless of how the infant appears (eg, even well-appearing young infants should be evaluated). These patients should not receive fever medication (eg, acetaminophen) until they have consulted with their health care provider.

●Children who are three months to three years who have a rectal temperature of 100.4°F (38°C) or greater for more than three days or who appear ill (eg, fussy, clingy, refusing to drink fluids).

●Children who are 3 to 36 months who have a rectal temperature of 102°F (38.9°C) or greater.

●Children of any age whose oral, rectal, tympanic membrane, or forehead temperature is 104°F (40°C) or greater or whose axillary temperature is 103°F (39.4°C) 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 100.4° F (38°C). (See "Patient education: Febrile seizures (Beyond the Basics)".)

●Children of any age who have recurrent fevers without any other symptoms for more than seven days, even if the fevers last only 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. In children who have had febrile seizures in the past, treatment of fever has not been shown to prevent seizures but is still a reasonable precaution.

Treatment of fever may be helpful if the child is uncomfortable, although it is not necessary.

Treatment not required — In most cases, it is not necessary to treat a child's fever. A child older than three months who has a rectal temperature less than 102°F (38.9°C) and who is otherwise healthy and acting normally does not require treatment for fever.

Caregivers who are unsure if their child's fever needs treatment should contact the child's health care provider. (See 'Evaluation recommended' above.)

FEVER TREATMENT OPTIONS

Medications — The most effective way to treat fever is to use a medication such as acetaminophen (sample brand name: Tylenol) or ibuprofen (sample brand names: Advil, Motrin). These treatments can reduce the child's discomfort and lower the child's temperature by 2 to 3°F (1 to 1.5°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 but should not be given more than five times in a 24-hour period. Acetaminophen should not be used in children younger than three months of age without consultation with a health care provider. The dose of acetaminophen should be calculated based upon the child's weight (not age).

Ibuprofen may be given every six hours. Ibuprofen should not be used in children younger than six months of age. The dose of ibuprofen should be calculated based upon the child's weight (not age).

Giving combinations of acetaminophen and ibuprofen or alternating acetaminophen and ibuprofen increases the chance of giving the wrong dose of one or the other of the medications and is not recommended routinely.

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

Increase fluids — Having fever can increase a child's risk of becoming dehydrated. To reduce this risk, caregivers 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 caregiver should consult the child's health care provider.

Rest — Having a fever causes most children to feel tired and achy. During this time, caregivers 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 they begin to feel better. Children may return to school or other activities when the temperature has been normal for 24 hours.

Sponging and baths — Sponging is not as effective as medications for fever and generally is not recommended. Alcohol should not be used for sponging because of the risk of toxicity if it is absorbed through the skin.

WHERE TO GET MORE INFORMATION — Your child's health care provider is the best source of information for questions and concerns related to your child's medical problem.

This article will be updated as needed on our website (www.uptodate.com/patients). Related topics for patients and caregivers, as well as selected articles written for health care professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.

Patient education: Fever in children (The Basics)
Patient education: Colic (The Basics)
Patient education: Febrile seizures in children (The Basics)
Patient education: Giving your child over-the-counter medicines (The Basics)
Patient education: Sepsis in adults (The Basics)
Patient education: Pneumonia in children (The Basics)
Patient education: Sepsis in newborn babies (The Basics)
Patient education: Adenovirus infections (The Basics)
Patient education: Juvenile idiopathic arthritis (The Basics)
Patient education: Mycoplasma pneumonia in children (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

Patient education: Croup in infants and children (Beyond the Basics)
Patient education: Bronchiolitis and RSV in infants and children (Beyond the Basics)
Patient education: Urinary tract infections in children (Beyond the Basics)
Patient education: Vaccines for infants and children age 0 to 6 years (Beyond the Basics)
Patient education: Febrile seizures (Beyond the Basics)

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Fever of unknown origin in children: Evaluation
The febrile infant (younger than 90 days of age): Definition of fever
Drug fever
Fever of unknown origin in children: Etiology
The febrile infant (29 to 90 days of age): Outpatient evaluation
Fever without a source in children 3 to 36 months of age: Evaluation and management
Fever in infants and children: Pathophysiology and management

The following organizations also provide reliable health information.

●National Library of Medicine

(medlineplus.gov/healthtopics.html)

●American Academy of Pediatrics

(www.healthychildren.org/english/health-issues/conditions/fever/Pages/default.aspx)

●The Nemours Foundation

(www.kidshealth.org/en/parents/fever.html, available in Spanish)

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