Gone are the days when one would shake that glass thermometer with a brisk snap of the wrist, then pop it into a sick child’s mouth. Now, digital thermometers are prevalent—in part for environmental concerns—and devices are available that can measure a person’s temperature in the ear, under the arm, or on the forehead.
Digital thermometers use electronic heat sensors to measure body temperature, and most can be used to take a temperature in a number of ways, including orally, rectally, or in the armpit.
A temporal thermometer is pressed against the forehead and uses an infrared scanner to measure the temperature of the temporal artery in the forehead. And a tympanic thermometer uses infrared rays to check the temperature inside the ear canal.
Accuracy can be tricky with ear thermometers—ear wax can get in the way —and the reliability of temporal artery thermometers can vary depending on the technique of the user. But such thermometers can be good alternatives for small children or older adults who can’t or won’t follow instructions to hold an oral thermometer under the tongue until it beeps.
Mercury health hazards
The Environmental Protection Agency and other medical, environmental, and government groups encourage consumers not to use old mercury thermometers—identifiable by their distinctive silvery bulbs—because of the potential for contamination if the thermometer breaks and mercury spills.
As of March 2011, the National Institute of Standards and Technology stopped calibrating mercury thermometers for both home and industrial settings, and more than a dozen states and municipalities have passed laws prohibiting their sale or distribution.
When mercury is released into the environment, it filters into streams and rivers and eventually to the ocean, accumulating in fish, and then in the humans who eat them. Mercury poisoning can cause damage to the nervous system, kidneys, and lungs.
Health officials caution not to throw old mercury thermometers in the trash. In some communities, hazardous waste collection facilities, pharmacies, or medical centers will accept old thermometers so they can be disposed of properly.
Getting the right readings
With cold and flu season looming, consumers need to be careful to use fever thermometers properly. Taking the temperature under the arm, for example, usually produces a reading about 1 degree lower in Fahrenheit than taking it orally. A rectal temperature reading is usually about 1 degree higher.
With children, the proper thermometer to use will vary with age. An older child can hold a thermometer under the tongue, but parents may need to use a rectal thermometer with a baby. Pacifier thermometers are available, but are generally considered less accurate.
And don’t forget: with a digital thermometer, you sometimes need to change the battery.