The Right Thermometers for Babies, Kids, and Adults
Whatever type of thermometer you choose, it should be easy to use and comfortable for you or your child. But some types of thermometers shouldn’t be used for certain age groups.
For Babies Younger Than 3 Years Old
The American Academy of Pediatrics (AAP) recommends taking a rectal temperature in infants and children younger than 3 months because it’s the most accurate. An armpit temperature can be easier, but it’s the least accurate, and Jennifer Shu, MD, a pediatrician in Atlanta and medical editor of the AAP’s website healthychildren.org, recommends thinking of an armpit temperature as a rough screening tool. Take an armpit temperature to see if your child may be running a fever, and if the temperature is above 99° F, double-check by taking a rectal temperature.
For Babies and Children 3 Months to 4 Years Old
The AAP doesn’t recommend using an oral thermometer for this age group because some children may have trouble keeping it in their mouth long enough to get an accurate reading. Once your child reaches 6 months old, an ear thermometer becomes an option. It gives quick results, but positioning it correctly can be tricky. Temporal artery thermometers, which read the infrared heat waves released by the artery in the temple along the side of the head, are the second-most accurate way to take a child’s temperature after rectally, according to the AAP, and they can be used for those of any age.
Note that some models come with probe covers, protective case covers, and other accessories that may pose a choking hazard for children. If the thermometer you buy includes small parts, keep them out of the hands of unsupervised children.
For Teenagers and Adults
Oral or in-ear/forehead thermometers (also called infrared thermometers) are convenient and give an accurate reading.
For Everyone
You may have heard or followed some rules about adding or subtracting a degree of temperature from whatever your thermometer says based on the method you used—adding a degree if you took an armpit temperature, for example. Shu says there’s no need to do this. Those tricks don’t add any accuracy to your thermometer reading.
Photo: Getty Images Photo: Getty Images
Types
We only tested infrared thermometers (for taking ear and forehead temperature) because these are generally the most expensive options. Digital stick thermometers are the other main type, used for taking oral, rectal, and armpit temperatures. Other types include digital pacifier thermometers, reusable forehead thermometer strips, and wearable (also called sticker) thermometers for kids.
Digital Stick Thermometers
A digital stick thermometer is the most widely sold and cheapest type. Look for one with an LCD that’s easy to read and a start button that’s easy to press. Many thermometers have an audible beep or other signal indicating that the reading is complete, meaning you won’t have to keep checking your watch. Digital thermometers rely on batteries to function.
Decide whether you want a rigid-tip or flexible-tip thermometer. The flexible types may be more comfortable, although many rigid-tip thermometers are designed to take underarm or rectal temperatures as well as oral temperatures. Not all flexible-tip thermometers can be used rectally, so you’ll need to read the labels. Use one thermometer for oral temperatures and a separate one for rectal readings. Be sure the thermometers are labeled so they’re not accidentally used for the wrong purpose.
Where: oral, underarm, and rectal (with the exception of some flexible-tip models, so be sure to read labels).
Infrared Thermometers
Some infrareds can be difficult to position, but they produce a temperature reading in just seconds. These thermometers are also among the most expensive.
Infrared tympanic thermometers measure the temperature inside the ear canal. Note that if an ear thermometer probe tip is cold, it can give you a cooler reading. Some models have a warming feature for better accuracy. Cold temperatures, say, from a child being outside, can also affect accuracy. This type of thermometer is quick and easy to use, and if plastic probe covers are included, it’s also very easy to clean. We did find that for ear thermometers that didn’t come with plastic probe covers, earwax buildup on the probe surface could significantly lessen accuracy. So if you choose a model that has no disposable covers, be sure to thoroughly clean the probe after each use.
Among the infrared ear thermometers we tested, half can also be used as temporal artery (forehead) thermometers by placing a cap that’s included over the probe and touching the cap to the forehead. This also avoids the cleaning issue because you’re not placing the probe inside an ear, and the cap holds the actual sensor slightly away from the skin.
Be sure to follow the specific technique recommended in the thermometer’s manual. Where to place the probe and how to move it are the differences that will vary from model to model.
A noncontact infrared thermometer (which became a common sight during the COVID pandemic) uses similar technology but isn’t made to be used in the ear. Instead, it typically works by holding the thermometer wand some distance from the patient’s forehead. If your child is restless, it may be difficult to get an accurate temperature. (We didn’t test any of these.)
Where: forehead, ear, or noncontact (depending on model).
Get Rid of Mercury
Glass thermometers wth mercury have largely been replaced by digital versions that don’t contain the potentially dangerous metal. But you may still have an old mercury thermometer or two lurking in a your medicine cabinet.
Mercury exposure can cause potentially deadly health problems if the thermometer breaks. So if you’re still holding onto a glass thermometer containing mercury (some glass thermometers contain alcohol), the AAP advises getting rid of it. (You can usually tell if a thermometer contains mercury because the interior fluid is a metallic silver, white, or gray. In the alcohol version, the fluid will be semi-transparent and red.)
Products containing mercury are considered hazardous waste, so you shouldn’t just throw an old mercury thermometer in the trash. Seal the item in a plastic bag and check with your local waste district or trash collector about disposing of it correctly. Use the recycling locator on Earth911.com to find a center that handles mercury near you.
Choosing a Thermometer
Thermometers can come with a range of features. Before you buy, know which ones best suit your needs.
Soft or Curved Tips
For ease of use and comfort, some digital stick thermometers have soft (flexible) or curved tips. Soft-tip versions can’t be used rectally, so read the packaging carefully.
Lighted Display
A large, backlit display and large digits can help you read temperatures at night or in low light.
Object Mode
Want to know that your baby’s formula or bath is at the right temperature? Some infrared thermometers allow you to measure the temperature of objects using a special mode that widens the allowed readings. (Our testers have not evaluated this feature.)
Fever Alerts
Some models will have a special beep when a temperature exceeds a certain level. Others have visual fever alerts, with the display changing color (green, yellow, red) to indicate temperature level. On some thermometers, you can mute any beeping so as not to wake a child if you’re taking their temperature while they’re asleep (or if they share a room with someone who is).
Memory
Some models record the last temperature or several temperatures taken, so you can track the direction your fever is going. Some newer models also offer app connectivity, allowing you to see temperature trends on your phone. Our testers didn’t evaluate these apps, though.
PHOTO: BRAUN
Age and Temperature Technology
A temperature that indicates a dangerous fever for one age group can be not so serious for another. This technology allows you to input the person’s age. A color-coded display tells you if the result is normal, elevated, or high for that age group.
PHOTO: BRAUN
Soft or Curved Tips
For ease of use and comfort, some digital stick thermometers have soft (flexible) or curved tips. Soft-tip versions can’t be used rectally, so read the packaging carefully.