Fever

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Fever is the most common reason children visit a pediatrician. Although it is extremely common, it is a source of concern for many parents. In most cases, however, fever is harmless and need not be feared. The fever is a symptom, not a disease, and the fever itself is not harmful. The brain will not let a fever rise high enough to cause brain or body damage. It is much more important to know what is causing the fever and to appropriately treat its cause, and how the child looks and acts overall is far more important than how high the fever is.

DESCRIPTION

Fever is defined as an elevation in body temperature above 100.4°F (38°C). While most people think of normal body temperature as 98.6°F, the normal range is actually between 97° and 100°F (many people, including children, have a natural rise in body temperature in the evenings to 99°-100°F). Exercise, hot weather, being dressed too warmly, or a hot bath can raise the body temperature up to 101.3°F (38.5°C). Warm foods and drinks can artificially elevate a temperature taken orally; if you suspect this, retake the child's temperature 30 minutes later.

Fever can be defined as:

  • A rectal temperature above 100.4°F (38°C).
  • An oral temperature above 99.5°F (37.5°C).
  • An axillary temperature above 99.0°F (37.2°C).
  • An ear (tympanic) temperature above 100.4°F (38°C) (if set in rectal mode) or 99.5°F (37.5°C) if set in oral mode. Note that tympanic thermometers are less reliable in younger children and not reliable in infants less than 6 months of age.

CAUSES

Fever is usually part of the way the body fights a viral or bacterial infection and is a good sign that the immune system is working to get rid of the infection. Fever helps the body to fight the infection (therefore it may be good to let the child have the fever as long as it is not making him uncomfortable). It is important to remember that fever is not an illness or disease, but a symptom. Teething does not cause a true fever (as defined above). There are other causes of fever besides common childhood illnesses; however, these fevers will be unusual in nature (how long they last, etc.) and will not follow the pattern described here. These can be discussed further with your doctor.

The height of the fever is not an indication of the cause or the seriousness of the cause of the fever, though bacterial infections are slightly more common in younger children with fever above 104°F. How the child is acting and feeling overall is far more important.

Fever is caused when the brain resets the thermostat, so to speak. Let's say the body is 98.6°F, and the brain decides that the body should be 102°F in order to fight an infection. The body is cooler than the brain thinks it should be, so the person gets chills and shivers, just like any other time that the body is colder than it "should" be, like being outside in winter, for example. This helps the body to warm up. When the fever "breaks" naturally or due to medication, the brain suddenly thinks the body should be 98.6°F, but it is still 102°F. The body starts to sweat in an attempt to cool off, just like on a hot day. That's why and when a fever causes chills and sweating.

TYPICAL COURSE

Most fevers from common childhood illnesses range from 101° to 104°F (38.3° to 40°C). It may go as high as 105°F. The body temperature is not harmful until it reaches 107°F (41.7°C), and a fever will not cause it to go this high; the brain's thermostat will not let a fever go high enough to be harmful.

Most fevers from viral illnesses (colds, flu, stomach viruses, roseola) will last from 2 to 4 days. The fever will rise and fall during the day and night. Treating the fever with medication may lessen the fever, but the temperature will rise again when the medicine wears off, and this is to be expected. The fever will continue until the underlying cause is treated or resolves, and repeat doses of medication may be needed. Do not wake the child up at night to treat the fever (because again, the fever itself is harmless). How the fever responds to medicine is not an indication of how serious the cause of the fever may be.

TREATMENT

Not all fevers need to be treated. If the child is uncomfortable (toddlers are often fussy or clingy and don’t sleep well), then treatment may make the child feel better and perhaps drink more fluid and sleep better. Remember, the fever is not a danger to your child, and it is helping her to fight the infection. You should only treat the fever if your child is uncomfortable (which may be manifested as crankiness or fussiness in a toddler). You should never use aspirin to treat a fever in children.

Plenty of fluids
Fever causes the body to lose more fluid through evaporation and sweating. Encourage plenty of fluids; popsicles and other fun, tasty fluids can be given. Watch for signs of dehydration; be sure your child makes some urine at least once every 8 hours.

Comfortable clothing
As discussed above, chills may occur as the fever rises, and sweating as the fever falls. In general, keep the room at a comfortable temperature and the child dressed comfortably, but not overbundled or overdressed. A blanket can be used when the child feels cold and then removed when sweating.

Acetaminophen (Tylenol®, FeverAll®, generic/store brands)
Acetaminophen can be given to children ages 2 months and above. It can be given every 4 hours. The dose to give depends on the child's weight; see our dosing chart for details. It can be expected to bring the temperature down a degree or two; it will not usually bring it down to normal.

Ibuprofen (Advil®, Motrin®, generic/store brands)
Ibuprofen can be given to children ages 6 months and above. It is given every 6 hours (it lasts a little longer than acetaminophen). It also tends to start working a little faster than acetaminophen, and bring the temperature down a little more (though not to normal). On the other hand, it has more side effects and less is known about its long-term effects due to the fact that it has not been around as long as acetaminophen. Both medications, as far as we know, are safe and effective. The dose to give depends on the child's weight; see our dosing chart for details.

Alternating acetaminophen and ibuprofen
This is popular with many parents, I suspect out of fear that the fever is harmful. In most cases, this practice is not necessary or recommended, for the following reasons:

  • With the knowledge that the fever itself is harmless, it is really not necessary to give both medications.
  • Giving both medications has not been tested and may have unknown side effects or risks.
  • It also increases the chance of making dosing errors, which can lead to an overdose.

Sponge baths/lukewarm baths
This is not usually necessary or recommended, though it may be a quick way to make a child more comfortable. If you are going to give a sponge or lukewarm bath to bring down the fever, keep the following in mind:

  • Give medication (acetaminophen or ibuprofen) at least 30 minutes before the bath, to reset the brain's thermostat (as discussed above). If you make the body colder than the brain thinks it should be, this will just make the child uncomfortable and cause shivering as the body tries to warm up again.
  • Be sure the water is not too cold. Use lukewarm water.
  • Never use rubbing alcohol or add rubbing alcohol to the water. This can cause a coma.

WHEN TO BE CONCERNED

If fever itself is relatively harmless, when should you be worried? It depends upon the age of the child:

Children 0-3 months old
A baby’s temperature needs to be taken with a rectal thermometer. This is the only reliable method for determining body temperature at this age. If a child this age has a rectal temp 100.4°F (38°C) or higher, then you need to call or see your doctor right away.

Children 3-36 months
Remember that the cause of the fever is much more important than fever itself. At this age, it is important to be able to identify a cause of the fever. Common causes are colds and flu (runny nose, congestion, cough) and stomach viruses (vomiting and diarrhea). If your child this age has a fever of 101°F or higher for more than 24 hours with no indication of an infection causing the fever then she should be evaluated. If she has symptoms of a cold or stomach virus, then be sure the child drinks plenty of fluid, treat with acetaminophen or ibuprofen if the child is uncomfortable, and treat the child's symptoms as appropriate. Fevers in this case usually last no longer than 3-4 days. If fever lasts longer than this, then the child should be evaluated.

Children 3 years and up
There are many infections in preschool and school age children that cause fever. Some of them do not cause any other symptoms. At this age, you do not need to be as concerned about a fever compared to younger children. If your child this age has a fever and the symptoms of a cold or stomach virus as described above, then treat the fever with acetaminophen or ibuprofen if the child is uncomfortable and give plenty of fluids. These fevers do not usually last more than 3-4 days. If she has a fever and no other symptoms, then it is usually best to wait 24-48 hours to see if other symptoms develop or if the fever resolves. If the fever persists without other symptoms, then she should probably be seen. At this age, keep an eye out for the symptoms of strep throat, which is common in school-age children. Symptoms include sore throat, fever, stomachache, nausea, vomiting, and/or headache. Not all children with strep throat have a sore throat.

Children of all ages
If the child is lethargic, difficult to arouse, or is acting abnormally, then the child should be evaluated immediately. Also if the child has a severe headache and/or a stiff neck, or any other symptoms which concern you then the child should be seen immediately. If the child is drinking fluids and perks up when the fever decreases and plays a little and smiles, this is a reassuring sign.

SUMMARY

  • Fever is our friend, helping the body to fight off infection.
  • The fever itself is harmless; it is important to know what is causing the fever.
  • If the child perks up periodically, is drinking fluids, and is more cheerful and playful when the fever comes down some, then these are very reassuring signs.

You should seek medical attention immediately if:

  • your child has a fever and is less than 3 months old.
  • a fever at any age is over 105°F (40.6°C).
  • the child is lethargic, acts very sick, is very irritable, is confused, has a stiff neck, a severe headache, or difficulty breathing.

You should see your doctor soon if:

  • your child is less than 3 years old has a fever more than 24 hours without an obvious cause.
  • your child is more than 3 years old and has a fever more than 48 hours without an obvious cause.
  • your child is less than 2 years old and has a fever between 104° and 105°F (40° to 40.6°C).
  • a fever goes away more than 24 hours and then returns.
  • the fever lasts more than 3-4 days.

Publication Date: 1/3/2005
Last modified: 1/3/2005
Last reviewed: 1/3/2005