Iowa Health Book: Pediatrics

How to Take Your Child's Temperature

This parent information aid on taking temperatures may be photocopied and distributed to parents without permission of the publisher.

Obtaining an accurate measurement of your child's temperature requires some practice. If you have questions about how to do it, ask a physician or nurse to demonstrate the procedure and then observe you as you do it. Several types of thermometers are available:

Digital thermometers

Digital thermometers record temperature with a heat sensor and run on a button battery. They take readings quickly, usually in less than 30 seconds, and display temperature in numbers on a small screen. They "beep" when they are finished taking the temperature. A student in Consumer Reports. found digital thermometers to be more accurate than glass thermometers. The same type of thermometer can be used to take rectal, oral, or armpit temperatures. I encourage you to buy at least one for your family. They cost about $10.

Glass thermometers

Glass thermometers with mercury have been in use since 1870. While they are the least expensive thermometers, they record temperature slowly and are often hard to read. To read a glass thermometer, find where the mercury line ends by rotating the thermometer slightly until the line appears. If you have difficulty reading a mercury thermometer, buy one with color zones.

Glass thermometers come in two forms: oral (mouth), with a thin tip, and a rectal, with a rounder tip.

Where to take the temperature

Rectal temperatures are the most accurate. Oral temperatures are also accurate if taken properly. Armpit temperatures are the least accurate, but they are better than no measurement.

For children 5 years of age and younger, rectal temperatures are preferred. Armpit temperatures are a second choice. For children over 5 years, oral temperatures are the usual method.

Before you use a glass thermometer, always shake the thermometer until the mercury line is below 98.6 degrees F. Also, always clean the thermometer with rubbing alcohol after each time it is used.

How to take rectal temperatures

Lubricate the end of the thermometer with petroleum jelly. Then:

• Have your child lie stomach-down on your lap.
• Lubricate the opening of the anus with petroleum jelly.
• Carefully insert the thermometer about one inch into the rectum. Never force it.
• Hold you child still, and press his buttocks together to hold the thermometer in place.
• Leave the thermometer in the rectum for two minutes with a glass thermometer, or approximately 30 seconds (until you hear the "beep") with a digital thermometer.
• Your child has a fever if the rectal temperature is over 100.4 degrees F.
• Practice taking rectal temperatures a few times when your child is not sick.

Place the tip of the thermometer in your child's armpit. The armpit should be dry. Evaporation of moisture from a damp armpit can have a cooling effect on the thermometer. Keep the thermometer in place by holding your child's elbow against the side of her chest for four minutes (five or six minutes for children over 2 years of age). If you remove the thermometer too soon, you miss a fever. If the armpit temperature is over 98.6 degrees F or you're uncertain about the result, recheck it with a rectal temperature.

How to take oral temperatures.

If your child has had a cold or hot drink within the previous ten minutes, wait to take his temperature until another ten minutes have passed.

• An accurate oral temperature depends on proper placement. Place the tip of thermometer under one side of the tongue toward the back. If you're not sure, ask a physician or nurse to show you where the thermometer should go.

• Have your child hold the thermometer in place with the lips and fingers, not the teeth. Clenching the teeth could break the thermometer.

• Tell him to breathe through his nose and keep his mouth closed. If he can't keep his mouth closed because his nose is congested, suction out the nose.

• Leave the thermometer in the mouth for three minutes with a glass thermometer or until you hear the "beep" with a digital thermometer.

• Your child has a fever if the oral temperature is over 99.5 degrees F.

Glass thermometers rarely break. If they do, they usually cause no harm, or only a superficial scratch on the lining of the mouth or rectum. The type of mercury found in glass thermometers is not poisonous. Call our office if you can't find all the pieces of glass.

Ear thermometers

Ear thermometers, now used by many doctors' offices and hospitals, read the temperature of the eardrum. The tip of the thermometer is placed in the ear canal. Eardrum temperature is as accurate or more accurate than rectal temperature. The ear thermometer has several advantages: it measures temperatures in less than two seconds, causes no discomfort, and requires no cooperation by the child (you can take the temperature while the child is asleep). It is much more expensive than other thermometers, however - about $99 for the home version.

Other ways

Temperature strips - liquid crystal strips that are applied to forehead - and temperature-sensitive pacifiers have been found to be inaccurate. They miss fevers in many children. Feeling the forehead also is not accurate. Fevers less than 102 degrees F usually can't be detected this way. Also, half of those children who feel warm to the touch don't have a fever. Disposable chemical-dot oral strips are accurate but must be kept beside the tongue for 60 seconds.

Adapted from: Schmitt BD: Your Child's Health, ed 2. New York, Bantam Books, Inc., 1991.

Dr. Schmitt is Director of General Consultative Services, The Children's Hospital of Denver, and Professor of Pediatrics, University of Colorado School of Medicine. He is a member of the Editorial Board of Contemporary Pediatrics.

Contemporary Pediatrics, June 1993, pp 83-84.

All contents copyright © 1992-1997 the Author(s) and the University of Iowa. All rights reserved.
Last Modified: December 02, 1996