Photo by Rebecca Tredway Photography
*I’m honored to host a series of guest posts by my friend Dr. Mark McColl to answer common questions about the seasonal illnesses that plague us this time of year. Dr. McColl is somebody I trust. Feel free to discuss these issues with the medical professional you trust, too.*
What is a fever? When does it become a problem? How should I treat it?
We use body temperature as one of many tools to help understand how sick a person is. Any number on a thermometer, in and of itself, doesn’t provoke a certain diagnosis or a specific set of therapies. It only tells us information we then use to help decide why the person has an atypical body temperature and if anything needs to be done.
Core body temperatures fluctuate during the day and often reach their peak in the late afternoon. A healthy adult might reasonably be measured at 99-100° between 4-5pm. Women attempting to time ovulation know their body temperatures change over the course of their menstrual cycle. It all has to do with what temperature is appropriate for the situation. One of the most critically ill children I ever cared for in the emergency room had a core body temperature of 94°. He had a brain infection that was so severe he couldn’t even maintain a normal body temperature. While people are individual in what their body temperature normally runs this doesn’t change how we define a fever. People who really are sick enough to manifest a fever still get about 100.4°.
So when do we worry about a rising body temperature? In infants we have to be more diligent because they lack many of the other signs and abilities we rely on in older children and adults to help point out the cause. An infant may be cranky or sleepy as a sign of their infection but lots of infants are occasionally extra fussy or take long naps. Unusual body temperatures help us tell the difference.
An infant less than 3 months old who develops a body temperature above 100.4°F should be evaluated by a physician in a matter of hours. They are at much higher risk of serious infections such as meningitis, urinary tract infections, and bacterial infections of the blood stream. As such, we must be all the more diligent to prove their fever isn’t of great concern. Hours matter in these situations so I often advise my patients who call in the middle of the night to seek emergency care if their infant has a fever. We must prove their health as the risk of fatal infection is so great.
In older children we move the ‘worry point’ to 102 F (~39 C). When children under three years of age but older than three months develop a fever they often display more evidence of why the fever occurs and if we need to try and fix it. They can report ear pain or sore throat. They may be potty trained and then suddenly develop accidents because of an urinary tract infection. They stop eating and complain of belly pain with appendicitis. In these situations we are able to focus in on the cause of their over all problem of which fever is simply one manifestation. I typically recommend to parents that children under three years of age be evaluated by a physician as soon as possible. Often the next day in the office is just fine as long as there are no other red flag symptoms like shortness of breath or uncontrolled abdominal pain. Emergency care may still be necessary. When in doubt contact your physician for advice on what to do for your particular situation.
As to everyone older than three years of age, it all depends on the circumstances. For instance, we are currently in the mini-epidemic of our seasonal influenza infections. In this case, anyone with a fever and symptoms at all suggestive of influenza ought to be evaluated. Early diagnosis and therapy can make a big difference in influenza outcomes. However, most of the year when otherwise healthy people have a modest fever such as 101 F, I recommend a watchful waiting approach. Respiratory tract infections typically are self-cured in seven days or so and other more serious infections will manifest with other symptoms that will help guide our diagnosis and therapy options.
A word on how to take an accurate temperature. What we want to know is what the temperature inside the body is. Rectal temperatures are by far the most accurate and it is what I recommend to parents caring for infants. As children age, oral temperatures are very good as children can hold the thermometer under their tongue consistently. Remember not to eat or drink anything for about 5-10mins prior as that can alter the result. If your kids are asleep it doesn’t matter what their temperature is really. I certainly wouldn’t wake them up to test it. Under arm or axillary temperatures are pretty good also. Lots of people suggest adding a degree to those readings. I’ve never seen good data to show that should be done so I always just ask parents how they took the temperature.
Ear thermometers and forehead thermometers seem like a great idea but I’ve seen many inaccurate readings. I once saw a healthy, playful 5 year old boy with ear pain who was reported to have a temperature of 108 F! Turns out the ear they checked the temperature in was infected. His body didn’t have a fever but his ear sure did.
So once you’ve found a fever and appropriate therapy is underway, whether that’s letting to body do its thing or using proper medication to kill off an invading pathogen, the question becomes “Should we reduce the fever?” I think the answer really depends on the person. Many kids can run around and play normally with all manner of fevers while others of us tend to feel really run down. I would say treat a fever when, after you know what’s causing it, you need it to go away. I don’t know of any real advantage to leaving the fever just for the fever’s sake. Sure many bacteria grow best in normal body temperatures so changing that might slow them down. In my experience though the body is so fantastic at doing what it needs to do that the body temperature doesn’t play the deciding factor.