Thermometers: Understand the options

Thermometers come in a variety of styles. Understand the different types of thermometers and how to pick the right thermometer for you.

By Mayo Clinic Staff

Choosing the thermometer that's best for your family can be confusing. Here's what you need to know about the most common thermometers.

Digital thermometers

Regular digital thermometers use electronic heat sensors to record body temperature. These thermometers can be used in the rectum, mouth or armpit.

Armpit temperatures are usually the least accurate. Rectal temperatures provide the best readings for infants, especially those 3 months or younger, as well as children up to age 3. For older children and adults, oral readings are usually accurate — as long as the mouth is closed while the thermometer is in place.

If you plan to use a digital thermometer to take both oral and rectal temperatures, you'll need to get two digital thermometers and label one for oral use and one for rectal use. Don't use the same thermometer in both places.

The pros:

  • Most digital thermometers can record temperatures from the mouth, armpit or rectum — often in a minute or less.
  • A digital thermometer is appropriate for newborns, infants, children and adults.

The cons:

  • Parents may worry about causing discomfort when taking a child's temperature rectally.
  • You need to wait 15 minutes after eating or drinking to take an oral temperature. Otherwise, the temperature of your food or drink might affect the thermometer reading.
  • It can be difficult for children — or anyone who breathes through the mouth — to keep their mouths closed long enough to get an accurate oral reading.

Digital ear thermometers

Digital ear thermometers, also called tympanic thermometers, use an infrared ray to measure the temperature inside the ear canal.

The pros:

  • When positioned properly, digital ear thermometers are quick and generally comfortable for children and adults.
  • Digital ear thermometers are appropriate for infants older than age 6 months, older children and adults.

The cons:

  • Digital ear thermometers aren't recommended for newborns.
  • Earwax or a small, curved ear canal can interfere with the accuracy of a temperature taken with a digital ear thermometer.

Digital pacifier thermometers

If your child uses a pacifier, you might want to try a digital pacifier thermometer. Your child simply sucks on the pacifier until the peak temperature is recorded.

The pro:

  • Your child may not even realize you're taking his or her temperature.

The cons:

  • Digital pacifier thermometers aren't recommended for newborns.
  • For the most accurate reading, your child must hold the pacifier still in his or her mouth for about three to five minutes — which is difficult for many young children.
  • Recent research doesn't support the accuracy of temperature readings from pacifier thermometers.

Temporal artery thermometers

Temporal artery thermometers — often sold as forehead thermometers — use an infrared scanner to measure the temperature of the temporal artery in the forehead.

The pros:

  • Temporal artery thermometers can record a person's temperature quickly and are easily tolerated.
  • Temporal artery thermometers are appropriate for infants older than age 3 months and for older children. New research suggests that a temporal artery thermometer also might provide accurate readings for a newborn.
  • Additional research suggests that temporal artery thermometers are the most accurate alternative to rectal digital thermometers for taking a child's temperature.

The con:

  • A temporal artery thermometer may be more expensive than other types of thermometers.

Mercury thermometers

Once a staple in most medicine cabinets, mercury thermometers use mercury encased in glass to measure body temperature. Mercury thermometers are no longer recommended because they can break and allow mercury — which is toxic — to escape.

If you have a mercury thermometer, don't throw it in the trash. Contact your local trash collection program to see if there's a hazardous waste collection site in your area.

Sept. 15, 2018 See more In-depth

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