A body's normal core temperature (one that is most accurately taken rectally) is 98.6 °F but a variety of factors (including age and general health) can influence a body's normal temperature. It is even common for a temperature to be slightly lower in the morning and then rise in the late afternoon. It is also common for strenuous exercise to slightly increase a body's core temperature. But when a core body temperature is greater than 100.4 °F, a fever exists. However, it is possible for lower values to indicate a fever, depending upon the child.

When your child has a fever in response to an illness, its occurrence is actually a beneficial thing, as it is during this time frame when there is an increase in white blood cells, antibodies, and other agents (e.g. cytokines) that fight the infections and cause an increase in the body's core temperature. So please keep in mind when a fever occurs, it is your child's way of trying to rid the body of the illness or infection it is encountering, which again is a good thing. Consequently, it is not always necessary for a fever to be treated if your child is playful and in good spirits, but please read on for more specifics on what exactly to do as it relates to your child's age and actual temperature.

As far as the best way to measure your child's fever, there are five different methods we would like to share with you:

  • Rectal: Up until 3 months of age, this is the most accurate way of measuring your child's temperature. Also, this is something you will see our staff do when the younger infants present for ill visits.
  • Oral: Best to use no earlier than 4-5 years of age.
  • Ear: Often employed for our older infants and children. It tends to run a bit lower than the rectal temperature but can give us a good idea of where things stand.
  • Axillary: An okay method when the child is older than 3 months of age, however, not as accurate as the rectal measurement.
  • Temporal: Measuring across the forehead; something we use in our office as long as the infants are greater than 3 months of age.

Now as far as what to do and expect if your child has a fever, let's break it down by age range:

  • 0-4 weeks of age: For anything greater than 100.4 °F rectally, this requires an immediate evaluation, whether it be to our office or after hours, to an urgent care facility or emergency room. Ultimately, expect an admission for evaluation of blood, urine, and cerebrospinal fluid (CSF — obtained via a lumbar puncture to look for meningitis).
  • 4 weeks-3 months of age: For anything greater than 100.4 °F, again, an immediate evaluation is needed but further care varies based on the evaluation and any diagnostic testing performed.
  • 3 months-6 months of age: Evaluate immediately for any fever greater than 102 °F, any fever lasting more than three days or sooner if your child is fussy/irritable, fever appearing at the end of an illness, or any rash not noted before the fever began.
  • 6 months-2 years: Please come in for an evaluation if the fever is greater than 104 °F, any fever lasting greater than three days, when the fever follows an illness or when no viral symptoms are noted (i.e. no runny nose, no cough, no vomiting and no diarrhea).

Now remember, with older children (even in the 1-2 year old age range), a fever does not necessarily need to be treated. If your child is in good spirits and playful and maintaining good hydration (drinking fluids and urinating plenty), fever treatment is not absolutely necessary. But if your child has a fever (no matter the number) and just not feeling good, it is okay to take the necessary steps to reduce the fever with the goal of bringing the temperature closer to the 100-101 °F range.

Some non-medication fever reducing measures include removing excess clothing, cool compresses to the forehead, armpits, and/or groin area, and lukewarm baths. As far as the medications (aka antipyretics), the medications include acetaminophen (Tylenol) and ibuprofen (Advil/Motrin). Some points to keep in mind include: Tylenol may be given every four hours but never more than five doses in 24 hours (and never give to children below 3 months of age unless instructed by one of us). Advil/Motrin may be given every six hours (but never to infants less than 6 months of age and more often closer to one year of age). We also prefer you not to interchange between the two medications, but if one doesn't seem to be effective, it is okay to use the other.

And never ever use aspirin to control a temperature in children. Secondary to its association with Reye's Syndrome, which is a condition that can affect children who have a viral infection, aspirin has the potential unfortunate outcome of liver failure and even death.