Fever is Your Friend!

A beloved Virology Professor, C. George Ray, uttered the immortal words “fever is your friend” during my training. He was not trying to discount the genuine concern, at times bordering on terror, which grips many parents at the first sign of a fever in their child. Rather, he was trying to get us, as Pediatric Residents, to think of fever as the messenger, not the BAD GUY!

First, some simple definitions: for this discussion, fever means a temperature of 100.5 degrees Fahrenheit (F), low-grade fever 99.5 to 100.4 degrees F. Human beings have a 2 degree F daily variation in their body temperature, 4 AM temperatures are typically in the mid-97 range, 4 PM temperatures usually in the low 99 range. Clearly then, a 99.5 degree F temperature at 5:30 in the morning would potentially have more significance than the same temperature at 5:30 in the evening.

So what is fever? Fever is this amazing inflammatory response that the body generates to help protect itself (NOT harm itself!) against the real bad guys, like bacteria and viruses. Guard cells detect the presence of one of these foreign invaders, and generate cytokines, or messengers, which travel to a specific area of the brain, the hypothalamus. The hypothalamus acknowledges the arrival of the cytokine by “turning up the heat.”

What’s amazing is that the “set-point” of the hypothalamus, that is, the degree of temperature elevation it will generate for a specific trigger, varies widely from one child to another, in large part based on the child’s age. Thus, an 11-month old baby who develops croup may have a fever of 102.8 degrees F, while her 5-year-old sister with the same virus has a temperature of 99.8 degrees F.

Dr. Ray used to caution us against asking a worried mother, when she awoke us at 2 AM with a fever call, what the temperature was. He joked that we were only trying to buy 2 minutes to wake up while she took the temperature. But his real point was that no specific temperature, by itself, should generate more alarm than another.

Dr. Ray taught us to instead ask things like, “Is the baby alert and responsive, making eye contact?” (The gallows line is “The child who looks you in the eye is not about to die.”) “Does she appear to be in pain?” “How is he eating?” “Is she having any trouble breathing?” Most children will have a significant fever at least once in their lives, yet for the vast majority of those kids, the high fever will not be associated with a life threatening illness. Therefore, answers to the questions above are far more important than the degree of fever in detecting the seriously ill child.

So how does fever help fight infections? By aiding in the elimination of the bad guys! Viruses, which cause most fevers, consist of two strands of either RNA or DNA, wrapped around each other. The virus is able to make further copies of itself only as long as those strands stay wrapped around each other. Fever causes the strands to unwind, stopping the replication of the virus, and the spread of the illness. And fever rather dramatically reduces the speed with which bacteria divide and multiply.

Knowing that fever actually helps your child shorten the course of the illness, what’s the best strategy for dealing with the fever? TREAT THE CHILD, NOT THE NUMBER! If your child is miserable and listless with a fever of 100.1 degrees F, give him a fever-reducer like acetaminophen or ibuprofen. If, on the other hand, the temperature is 102 degrees F, and your son is running around like nothing ever happened, then maybe it doesn’t need to be treated.

In fact, the best strategy might be no thermometer at all, relying on your hand to decide fever is present, and your child’s degree of discomfort to decide when medication is necessary. “But,” you say, “won’t a high fever hurt Laurie’s brain?” A very high fever, in the 107 degrees F range, caused by a very specific illness (and which I have, in 37 years of doing Pediatrics, never seen) could harm the brain. With a normal intact brain, the body will virtually never produce a fever above the 105 degrees F range. I have seen thousands of 105 degrees fevers; no one was harmed by it. Again, look at the child. If she’s 105 degrees and unresponsive (or 100.5 degrees and unresponsive!) , go to the Emergency Department; If she is miserable, but alert, in no pain or respiratory difficulty, you can afford to observe at home, checking in with the Clinic at any time you have a concern.

Which medication to use? Both acetaminophen (every 4 hours) and ibuprofen (every 6 hours) work very well, ibuprofen producing a fraction of a degree more decrease in fever than acetaminophen (brand name Tylenol). In general, I recommend staying with one medication or the other. If a child has had a previous febrile seizure, which means a subsequent fever may produce another seizure, alternating the two medications at 3-hour intervals is reasonable.

A few caveats: Ibuprofen can damage the kidneys if a child is dehydrated. Therefore, I recommend it never be used if your child is vomiting, or drinking very poorly. And both medications should be limited to a maximum of 4 doses in 24 hours (even though acetaminophen could theoretically be given 6 times in 24 hours). Use the dose on the box, unless your medical provider has given you an alternative dose (we base our doses on weights, which are more accurate, the manufacturers use a conservative dose for age, so typically they will be a bit lower than the dose I might suggest).

I have tried to reassure you that fever is an important, harmless component of the body’s infection-fighting machinery. Because it can be associated, infrequently, with serious infections, every parent MUST be comfortable with how their feverish child appears to them; if you don’t feel comfortable, you should immediately contact your medical provider for advice. Ultimately, the fever will not harm your child, but the infection that caused it could.