My Baby's Got a Fever!

by Herschel Lessin, MD

chunky baby legsIt's 2 a.m. in the middle of January, and the phone rings -- again! As I groggily write down the message from the answering service, I marvel at its similarity to many of the others, particularly at the height of the winter season. "Doctor, my baby has a fever..."

Misinformation about fevers and whether to treat them abound. One of the most frequent reasons parents call or visit a pediatrician is when their child has a fever. But what is a fever, and what actually causes it?

What is a Fever?

Normal body temperature
Normal body temperature is 98.6° F, but this is just an average. Some people are normally higher, and some are normally lower. A fever is defined as a body temperature above 100.5° F Therefore, a body temperature of 99.5° or 100° F is not a fever and should not be a cause for worry in otherwise normal children.

Body temperature and infection
Body temperature is controlled by the hypothalmus, a section of the brain that acts just like your household thermostat. If the body gets too cold, the thermostat sends out instructions to warm things up, and if it gets too hot, the thermostat tries to cool things down. When the body is faced with an infection, a chemical messenger known as endogenous pyrogen acts to reset the thermostat to a higher temperature -- in other words, it causes a fever.

Fever can therefore be thought of as one of the body's normal responses to infection. And like most things that happen naturally in our bodies, it doesn't occur just for the heck of it. There is usually a good reason. Because the increase in body temperature plays a role in helping the body's defenses fight off infection, we may have to reconsider the need to "treat" fever.

Taking Temperatures

Ear canal thermometer, arguable accuracy
The new high tech ear canal thermometers are remarkably fast and easy to use. My personal experience is that they tend to read a little bit high, especially with higher temperatures, which may scare people.

Rectal thermometer, the most reliable method
The only really reliable way to take a young child's temperature is with a rectal thermometer. Feeling the forehead is just not trustworthy, and young children are rarely able to tolerate oral thermometers. They can't keep them under their tongues, and they breathe around them, resulting in artificially low readings. An axillary (armpit) temperature takes at least 10 minutes and is quite inaccurate as well.

In older children, the temperature reading is usually not as critical. It's often enough to know if the reading is high (over 103° F) or not. In very young infants and children, however, the actual number is more important. Although taking a rectal temperature is not a lot of fun for either parent or child, it is the method that has proven most accurate.

Should Fever Be Treated?

Recent evidence has shown that fever in children may play a role in fighting disease. As parents, should we treat fever?

Not all children's fevers need treatment. A temperature lower than 100.5° is not a fever and does not need medicine. Most children with temperatures lower than 102° generally do not feel all that bad. Earaches and sore throats may hurt, but just having a fever does not cause much discomfort. Fevers of 102° or less, by themselves, do not routinely need treatment if the child feels and acts relatively normally. The increased body temperature may actually be of benefit in fighting off the infection.

Children with temperatures above 102° are often uncomfortable because of the fever and may need treatment. The main reasons to treat fever are, first, to make the child more comfortable, and second, to help you evaluate how sick he looks after you get his temperature down. A child with a fever who is feeling and behaving well does not need to be given medication.

There are many ways to treat fevers in children, some good and some not so good.