Thermometers: Understand the options
Medically reviewed by Drugs.com. Last updated on Nov 7, 2022.
Choosing the thermometer that's best for your family can be confusing. Here's what you need to know about the most common thermometers.
Types of thermometers
In general, there are two types of thermometers. Touch, or contact, thermometers must touch the body in order to measure temperature. Remote, or no contact, thermometers can measure body temperature without touching the skin.
The most common kind of contact thermometer uses electronic heat sensors to record body temperature. These thermometers can be used on the forehead, mouth, armpit or rectum. Most electronic thermometers have a digital display that shows you the temperature reading.
Rectal temperatures provide the most-accurate readings for infants, especially those 3 months or younger, as well as children up to age 3. Temperatures taken from the armpit are usually the least accurate. For older children and adults, oral readings are usually accurate — as long as the mouth is closed while the thermometer is in place.
- Most electronic contact thermometers can record temperatures from the forehead, mouth, armpit or rectum — often in less than one minute.
- An electronic contact thermometer is appropriate for newborns, infants, children and adults.
- 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.
If you plan to use an electronic contact thermometer to take both oral and rectal temperatures, get two thermometers and label one for oral use and one for rectal use. Don't use the same thermometer in both places.
Many schools, businesses and health care settings are screening visitors for fever. A remote thermometer that doesn't require skin contact allows people to remain further apart. Remote thermometers can be used on the forehead (temporal artery) or the ear (tympanic).
Temporal artery thermometers
Remote forehead thermometers use an infrared scanner to measure the temperature of the temporal artery in the forehead.
- A remote temporal artery thermometer can record a person's temperature quickly and are easily tolerated.
- Remote temporal artery thermometers are appropriate for children of any age.
- A temporal artery thermometer may be more expensive than other types of thermometers.
- This type of thermometer may be less accurate than other types. Direct sunlight, cold temperatures or a sweaty forehead can affect temperature readings. Variations on user technique, such as holding the scanner too far away from the forehead, also may affect accuracy.
Remote ear thermometers, also called tympanic thermometers, use an infrared ray to measure the temperature inside the ear canal.
- When positioned properly, infrared ear thermometers are quick and generally comfortable for children and adults.
- Infrared ear thermometers are appropriate for infants older than age 6 months, older children and adults.
- Infrared ear thermometers aren't recommended for newborns.
- Earwax or a small, curved ear canal can interfere with the accuracy of a temperature taken with an infrared ear thermometer.
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.