Fevers are responsible for roughly a third of all visits to pediatric offices, numerous emergency room visits, and a great deal of parental anxiety. Let’s talk about why fevers happen, what you should look for, and what (if anything) you should do.
We all learned in elementary school that the normal human body temperature is 98.6 degrees F (37 C). In reality, it’s not that simple; a normal body temperature falls within the range of 97.0-100.4 F (36.1-38 C). Your body temperature is controlled by a thermostat (officially dubbed the “anterior hypothalamic nucleus,” but we’ll stick with “thermostat”). Just like the one in your house, the body’s thermostat allows small fluctuations in temperature to occur all the time. If your home thermostat tried to keep your house at exactly 72 degrees F (“room temperature” C), it would be cycling on and off several times a minute, and you would need a new one within a month. In the same way, if you go outside on a hot day, your body temperature starts to creep up until it reaches a threshold where the thermostat takes measures to bring it back down; you go back inside your air-conditioned house, and your body will soon adjust the other way. Your temperature also varies to a small degree with the time of day–usually about a degree warmer at 3pm than at 3am.
A fever is defined as a core body temperature over 100.4 F (38 C). Any temperature under 100.4 F (38 C) is not a “low-grade fever;” it’s normal. If your child does have a fever, it’s one of several signs that may indicate that his body is fighting an infection. The fever itself is harmless–really, it’s helpful, as it is part of the body’s immune response, serving to weaken viral and bacterial infections. Even the height of the fever isn’t too concerning; the temperature doesn’t necessarily correlate with the severity of the illness. Young children, especially, often have high fevers with viral illnesses that cause only mild symptoms. Remember that a fever caused by illness, no matter how high, will not damage your child’s brain or cause any other permanent harm. Some children do have “febrile seizures,” which are typically short seizures caused by fever. However, these seizures tend to occur at the very beginning of a fever, when it would have been impossible for the parents to know it was coming. Trying to keep a fever down to prevent seizures is not necessary.
Because fever in an infant less than 2 months of age may be the only sign of a life-threatening illness, fever reducers should not be used in children under 2 months of age. (We don’t want to cover up a warning sign.) These very young infants are a special group because their immune systems are immature, leaving them susceptible to infections that may be fatal if untreated. A rectal temperature is the only accurate way to measure an infant’s temperature; if your infant under 2 months old has a rectal temperature over 100.4 F (38 C) or under 97 F (36.1 C), call your doctor or go to the emergency room immediately.
In older infants and children, the exact temperature is not as important. Ear and temporal thermometers are quick, non-invasive, and accurate enough for these children. There is no need to add a degree to the temperature reading on your thermometer. Feeling for a fever with your hands on a child’s forehead is notoriously inaccurate (although studies have shown that moms are more likely to be right than doctors). If your child feels warm, go ahead and check with a thermometer.
A couple common questions about fevers involve teething and immunizations. Many parents believe that teething causes fevers in infants, but there is no great evidence that teething causes fevers. The most likely reason for the connection is that children who are teething are also at an age where they are constantly exposed to new viruses (especially if they are in daycare), and they happened to have both at the same time. However, we know for certain that vaccines do cause fevers. Many children will have a fever within 24 hours or so of getting their shots; this may last a day or two. With live-virus vaccines (MMR and chickenpox), this may happen a few days later. Many parents will give Tylenol or ibuprofen after–or even before–immunizations to treat this fever. But doing so may reduce the vaccine’s effectiveness, as these medicines blunt the body’s immune response (which is required for vaccines to work). It’s best to avoid giving your child medications to prevent a fever from immunizations. If she has a fever and is miserable later, you can always give it then.
When To Check
Unless you are a nurse with OCD tendencies, you probably don’t routinely check vital signs on your children–and there’s no need to. The following is a list of times when you might consider checking your child’s temperature:
– If your child feels warm to touch.
– If your child is abnormally fussy or not eating well.
– If your child has other signs of illness (vomiting, diarrhea, cough, rash, etc.).
When To Worry
If your child is less than 2 months of age, a fever is always concerning (see above). Otherwise, your child’s symptoms and appearance matter far more than the fever itself. If your child has a fever but is running around the house playing pirates vs. princesses (or otherwise acting more or less normal), it’s probably safe to wait it out. However, you may need to seek urgent medical attention if your child:
– is having difficulty breathing.
– has severe vomiting or diarrhea, and you can’t get her to drink fluids.
– is difficult to wake up (lethargic), or has a stiff neck and headache.
– has had a fever for 5 days or more.
– has a fever after spending a long time outdoors in the heat.
– has any medical conditions that make him more susceptible to infections.
Also, please contact your doctor immediately or go to the emergency room if you have urgent concerns about your child’s health.
What To Do
Relax. Unless your child has any of the urgent problems above, you’re probably fine to wait until the morning, when you can call your pediatrician if you are still concerned. Remember that fevers are a natural part of the body’s immune response, and are helpful for fighting infections; they don’t harm your child. Even so, a fever can certainly make your child feel terrible, and many parents want to bring the temperature down. Sitting in a lukewarm bath is a good way to do this, and for otherwise healthy children, the occasional use of fever reducing medications is safe as well:
– Acetaminophen (Tylenol) may be used in children over 2 months of age. Click for dosing.
– Ibuprofen (Advil or Motrin) may be used in children over 6 months of age. Click for dosing.
– Aspirin should not be used in children.
The other aspect of treating fevers is to treat the cause, if necessary. Most fevers in children are due to viral illnesses, which typically go away on their own in 3-7 days. In these cases, we treat the child “symptomatically,” which means we try to keep him comfortable until the virus runs its course. Sometimes, children have bacterial infections (pneumonia, ear infections, urinary tract infections, etc.) that need antibiotic treatment. Your pediatrician will need to see your child to diagnose these infections and determine whether antibiotics are needed.