Fever....Do I need to Worry?

What exactly is a fever? When do I need to be worried?  Do I need to give medicine? Will my child have a seizure? Will the fever cause brain damage?…..

Disclaimer: This blog entry regarding fever is for children over the age of 2 months.  If your child is less than 2 months old and has a rectal temperature of > 100.4, call your doctor immediately

     Fever…One of the biggest anxiety producers for most of us.  In fact, as many as 30% of pediatrician office visits are related to the complaint of fever alone.   It has caused so much anxiety amongst parents(yes, even in my household), that the term “fever phobia” was coined in 1980 to describe parental concern over “low grade fevers”. 

     Before we go in to what causes a fever, we should first figure out what temperature IS a fever.  People have been asking this question for a long time.   In 1868, a guy by the name of Carl Wunderlich reported that 98.6°F(range: 97.2 – 99.5°F) was the average adult temp after looking at 1 million temperature readings of 25,000 patients via a foot-long(!!) thermometer used in the underarm. Interestingly, since then, many studies have shown that under normal circumstances, body temperature varies as much as 0.9 °F, being lowest in the morning (between 4 and 8 am) and peaking in the early evening (between 4-6pm). Body temp can also vary somewhat with a  variety of specific individual and environmental factors, including age (slightly higher in young infants), sex, physical activity, and ambient air temperature.

     The other compounding factor is that the “normal” temperature can change depending on the site in which you take the temperature.  I will be the first person to confess that I prefer the kiss or touch to the forehead method.  The PTSD that my children already have is obvious when the crying and screaming starts as soon as they see the thermometer.   So, I did a little digging to figure out if there has ever been a study done on parental touch and prediction of fever.  And, surprisingly, there HAS been such a study.  The study showed that parents were not actually good at predicting if there was a fever but could tell you that their child did not have a fever.   So, we are pretty good a feeling a child and saying for sure they don’t have a fever(I guess when they are really cool), but aren't as good at predicting if the temperature is a true fever. So, unfortunately, we have to use a thermometer.  But, what kind and where?  

     According to the textbooks, the best place to take a temperature is within the heart or the lower esophagus.  Now, if only it were that easy, right?   As we saw in the 1868 study, the underarm was one of the first locations used for temperature measurement.  The pro here is that it is easy to take with the least amount of discomfort for your younger child.  The con with the underarm temp is that skin temperature can lag behind changes in core temp. For older(>5) children,  taking the temperature under than tongue is also  easy and painless and the oral temperature has less lag time than the skin.  This temperature, however, may be affected by mouth breathing or recent ingestion of hot/cold food or drink. For younger children, especially infants, the rectal temperature is the gold standard because there is less deviation from environmental factors.  The con with this method is the obvious discomfort (and in my children, PTSD).   So what about those ear thermometers?  Unfortunately, the accuracy is debatable due to difficulty aiming the thermometer at the exact spot on the ear drum. The temperature reading can also be affected by ear wax as well as an ear infection.   Finally, as if there wasn't enough options, there are the newer temporal (forehead) thermometers.  Aside from them being cost-prohibitive, they can also not be as accurate as the oral and rectal methods.  They are great for a screening method but an alternate method should be used to confirm a fever.  My recommendation is to choose a consistent form of measurement and take the measurement in the same site to monitor changes in body temperature. 

 I have listed the normal temperatures below for each method:

Normal temperatures:

-      Underarm: – 97.5°F (average) – range 94.5-99.1  (Fever is > 100°F)

-      Oral – 97.9°F (average) – range 95.9 – 99.5 (Fever is > 100.4°F)

-      Rectal: 98.6 °F (average) – range 97.9 – 100.2 (Fever is > 100.4°F)

-      Tympanic(Ear) : 97.9°F (average) – range 96.3 – 99.5 (Fever is > 100.4°F)

-      Forehead :  Currently not studied.

     Ok, enough about taking a temperature, the big question is what causes fever?  Fever occurs when the body responds to chemicals release by toxins, infections, bacteria/viruses themselves.  The body responds by resetting the brain’s thermostat which eventually results in an increase in core body temperature.  In short, it is the body’s way of causing a hostile environment for the bugs within us.  (Fever = something good the body does to help fight infection)

     So we know fever can be a good thing, but the real question is, when do I need to worry?  Debate has surrounded in the medical community as to whether the height of the fever is associated with worse outcomes or if it predicts a more serious illness.   Some studies show that a temperature >106°F(Rectal or oral) is associated with a higher incidence of serious illness so this is the temperature I tell most parents to worry about. 

     Clinical appearance, rather than the height of the fever, is a more powerful predictor of the seriousness of the illness. Interestingly, a child with a fever can have an increase in both heart rate (10-15 beats/min per 2°F) and respiratory rate( 3-5 breaths per minute per 2°F).  This is one case where treating the fever with medicine may help.  By lowering the temperature, you are better able to assess if the child has increased heart and respiratory rate from the illness versus the fever.

Two of our most common questions are the following:

If my child’s fever goes to high, will it cause them to seize?  For the 2-4% of children who develop febrile seizures, the height of the temp has been shown to be independent of risk factors.  Basically, for those children who are going to have a febrile seizure, it can happen at both high and low temperatures.  Therefore, for those children who will have these seizures, neither the height of the fever nor if the fever is treated with medicine matter. 

Will a high temperature cause permanent brain damage?  Fortunately, this has not been shown to be caused by a fever (even a temp as high as 107.6) associated with infection, it is the underlying illness rather than the fever itself that is responsible for  the most complications.

Now the big question….Your child has a fever, they are crying and feeling awful, what do you do?

     Although fever may have some beneficial effects in terms of shortening the duration of illness by creating an unfavorable host environment for the infecting microbe, this effect usually is outweighed by the associated increased metabolic demand and discomfort of the child. As stated above, parents should not focus solely on the height of the fever, but if the child becomes uncomfortable or cannot be assessed clinically, fever should be treated. My advice to parents is usually to treat your child not the number on the thermometer.  If your 2 year old is running around the house faster than you and has a 102 then you probably don’t need to treat their fever.

      Because of the increased energy demand from the fever, children with fever should be given proper hydration. (Yes, Grandma was right – you need to drink plenty of fluids!)

     However, one area that grandma may have been wrong about is putting your child in the tub to get rid of the fever.  Sponging or bathing with lukewarm water provides only marginal temperature reduction and is often accompanied by discomfort and shivering. Cold water or rubbing alcohol should not be used because it leads to vasoconstriction(less blood flow) rather than to vasodilation(more blood flow)  that is need for heat dissipation. Thus, the temperature can actually rise.   Alcohol can also be absorbed through the skin and can cause toxicity

     In terms of treatment, either Tylenol or Ibuprofen can be used.  Ibuprofen, in some studies, has been shown to be a slightly better overall fever reducer and can last longer. However, there is a recent study out that does raise some concerns regarding large amounts of ibuprofen causing kidney damage in children under the age of 5. There are currently no concrete recommendations as to what this study means for the future of fever management.  For now, it is still recommended that either is ok as long as they are used in moderation and your child remains hydrated.  (Disclaimer #2: please check with your doctor regarding proper dosing if your child’s age/weight is not on the box.  Also, please check with your doctor, prior to giving medicine, if you child has any chronic health conditions including, but not limited to,  liver problems, kidney problems, or bleeding disorders)

    So, you gave the Tylenol and your child’s fever is better, can I stop worrying?  Mis-advice is given here all the time.  Often doctors and nurses will tell parents to worry only if the fever doesn’t go down with medicine.  However, it has been shown that response of fever to antipyretic(anti-fever) therapy should not be used as a prognostic factor for determining whether the child has a less serious illness.  Several studies have shown that fevers even due to serious infection can respond to medicine. However, because it is often difficult to assess a child who is having discomfort from fever, treating the fever may allow better assessment of the child.   A child who has a serious infection often continues to look ill even after fever reduction, whereas the appearance of a child whose illness is benign (non-life threatening) usually improves.   On the flip side, non-serious viral infections can cause a fever to persist even despite medicine.   The key, as above, is to treat your child, not the number.   If your child looks ill despite medicine, then they should be evaluated by a doctor.  When in doubt, call your pediatrician J 

     Another quick point of discussion is the use of combination/alternating therapy  of acetaminophen and ibuprofen. A variety of alternating regimens has become a popular practice for most parents.  However, the only study that suggested an advantage of alternating therapy used the incorrect dosing the children who were getting single therapy.  The con here is that alternating antipyretics may be confusing and has the potential for increased risk of toxicity. The other concern is that ibuprofen inhibits certain enzymes in the body that digest acetaminophen, therefor, children who are dehydrated have a higher risk of acetaminophen toxicity when given both.

In Conclusion...

Fever is the body’s way of attacking its offenders.  Left alone, the fever might even help your body to fight an infection faster.  That being said, none of us like to feel miserable and neither do our children.  Therefore, if you child has a fever and feels bad, medicine could be given.  The main point here is treat your child not the thermometer. 

    Importantly, neither the height of the fever nor the fever’s response to medicine predict if your child is fighting a more or less serious illness. When in doubt, call your doctor’s office.  We are here to help!!
(I know this was a very short conclusion for a very long blog entry, but there is so much good stuff in this one that it was hard to conclude it with a short summary!)

So....when should you worry or have your child seen?

1) You child is < 2 months old and has a rectal temperature of > 100.4 – be seen immediately!

2) Your child is ill appearing even after use of Tylenol/Motrin

3) Your child has a fever lasting longer than 3-5 days

4) Your child has an obvious source of infection (ear pain, sore throat with puss, etc)

5) Your child has a chronic illness, a cardiovascular or pulmonary disease, an  immature or suppressed immune systems, or an underlying anatomic abnormalities

6) When in doubt, call the office, we can talk you through it!


Dr. M

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