Fever in babies

Fever—especially a high fever in a young baby—can be worrisome for parents and doctors alike. Pediatricians consider 100.4 degrees Fahrenheit or above to be a fever. Fever is an elevation of body temperature that is usually caused by pyrogens, chemicals that are released into the blood stream from the cell walls of bacteria or from white blood cells when the body is infected by a virus or bacteria. The chemicals cause the hypothalamus, a part of the regulatory center of the brain, to reset the body’s temperature temporarily.

How do you know if your baby has a fever? The easiest way is to take his temperature. But parents can often tell even without a thermometer. Usually, the baby will lose his appetite, may vomit, may be listless or fussy, and may be hot to the touch. New parents worry they will not know when their baby is sick, but parents quickly learn when their baby is “off”.

Taking your baby’s temperature

If your baby is under eight weeks of age, it is important to know his exact temperature. We usually ask parents to take a rectal temperature in this case. When the baby is older, thermometers that gauge temperature in the ear, armpit, or on the skin are also acceptable. You should add a degree to a temperature gauged via the armpit or skin.

Treating a fever

Fever in and of itself is not harmful to the body. In fact, fever is usually a result of the body responding to an assault on the immune system. The body is trying to kill the bacteria or virus by rallying the body’s immune system.

The main reason to treat fever is for comfort.

I often suggest putting a baby with a fever in lukewarm water first to cool him down. You may find it easiest to get in the tub with the baby. Slowly add lukewarm water to the bath. It may take 15 to 20 minutes to get the fever down. If the baby starts to shiver, increase the temperature of the water until he stops shivering. Of course, be careful not to burn him.

Then once the baby is cooler, you can give acetaminophen (Tylenol) according to your baby’s weight. If he is over six months of age, you can use ibuprofen (Advil or Motrin), again according to his weight. There is no evidence that alternating ibuprofen with acetaminophen helps more than taking just one or the other.

When to call your doctor

It is common for babies to have a fever for the first forty-eight hours of an illness. To best evaluate how sick your baby is, I recommend trying to get his temperature down first, as most babies look pretty sick if they have a high temperature. Once the fever is down, you can get a better sense of what is ailing your baby.

You should contact your doctor if your baby has a fever and is under eight weeks of age, has been sick for a while and then develops a fever, if the fever is 102 degrees or higher, if the baby does not look well, or if you feel uneasy about any aspect of your baby’s demeanor or appearance.

Has your baby had many fevers? How have you treated them? Any tips for other parents?

Dr. Victoria McEvoy graduated from Harvard Medical School in 1975 and is currently an Assistant Professor of Pediatrics at HMS. She is the Medical Director and Chief of Pediatrics at Mass General West Medical Group. She has practiced pediatrics for almost thirty years. She has been married to Earl for thirty six years and raised four children. She currently enjoys writing, traveling, reading, almost all sports, and spending time with her two grandsons.

Family Health Guide
To take advantage of the latest medical advances, and to deal with the often-confusing world of health care, you need information that is clear, accurate, easily understandable, and accessible. The Harvard Medical School Family Health Guide brings you the information you need to keep your and your family healthy and to cope with illness when it does strike. 170 faculty members of Harvard Medical School, physicians who care for patients every day, developed this comprehensive guide.

Do you have a baby? Connect with others with similar health concerns and issues. Click here to join the group.

This content is not intended to substitute for personalized medical advice, diagnosis, or treatment from your healthcare provider. Read our full disclaimer.