Your kid seems tired, cranky and out of sorts. Their forehead feels hot to your hand, so you decide to check if they have a fever. What type of thermometer should you use and how should you take their temperature to make sure it’s most accurate? Pediatric nurse practitioner Melanie Klein, CNP, breaks down which thermometers to use for kids of any age.
Different types of thermometers
The accuracy of a thermometer is largely affected by your child’s ability to allow for the use of the right tool for the job.
“Older children and teens can use an oral digital thermometer without difficulty, but infants and young children don’t have the motor skills or patience to get an accurate reading from that kind of thermometer,” says Klein.
When considering which thermometer to use, there are several options to choose from.
Standard digital thermometer
These thermometers read your body temperature through the small metal tip at the end of the thermometer. They’re quick, easy and inexpensive. By placing the tip under your child’s tongue, in their armpit (axillary) or inserting it rectally, the thermometer can pick up your kid’s temperature with varying degrees of success.
Using the axillary (armpit) method will be the least accurate method because it’s not measuring your kid’s temperature from the inside of their bodies. Plus, most axillary skin and tissue aren’t close enough to major blood vessels to get an accurate reading. If you do an axillary temperature reading, you’ll want to add 1/2 to 1 degree Fahrenheit (.3 to .6 degrees Celsius) for a more accurate reading.
For children 3 years old and younger, a rectal temperature is the most accurate for a standard digital thermometer. For kids 4 and up, an oral temperature reading is most accurate.
“You should have separate oral and rectal thermometers and they should be labeled to prevent cross-contamination,” advises Klein.
Digital ear thermometer
Digital ear thermometers use infrared technology to capture the temperature of your eardrum. These are most helpful if your child is 6 months to 1 year of age.
Though less invasive than a rectal temperature reading and easier for older kids, you want to make sure your kid’s ear canal isn’t blocked up with ear wax and that you’re able to insert the thermometer effectively.
“You don’t want to use this to check their temperature shortly after coming in from the cold because it might not be accurate,” notes Klein. “Instead, wait five to 10 minutes until they’re warmed up and acclimated to the room temperature before using this thermometer.”
Digital forehead thermometer
Similar to ear thermometers, these use infrared technology to measure heat waves coming off your kid’s temporal artery. This major artery runs across the middle of your forehead just below the surface of your skin. Like the axillary method, it’s not as reliable as a rectal or oral temperature reading, but it can be used for kids 3 months and older. Keep in mind, if your child is sweating or has just come in from outside, that could affect the accuracy of this temperature reading, too.
Never use these thermometers
There are some thermometers you never want to use when checking your child’s temperature. These include:
- Mercury thermometers: These aren’t recommended because the casing that holds mercury (a toxic chemical) is made of glass and could easily break. If you do own a mercury thermometer, you should call a local trash collection service to find out how to properly dispose of it before throwing it away.
- Forehead strip thermometers: These sound easy — you just press them against your child’s forehead and get a temperature reading in under two minutes. But they’re largely inaccurate. According to The Centre for Evidence-Based Medicine at the University of Oxford, these thermometers don’t detect 4 out of every 10 fevers.
- Pacifier thermometers: These are really hard to use accurately. In order for them to work, they shouldn’t be used 15 to 30 minutes after your kid eats or drinks and they need to be actively sucked on or held in an infant’s mouth for three to five minutes to get a steady reading. These are never recommended for newborns.
Best way to take an accurate temperature
A normal body temperature is about 98.6 F (or 37 C). A fever is considered to be a temperature of 100.4 F (38 C) or above.
You can treat a fever at home with a fever reducer medication and fluids to make your child more comfortable, or let it run its course. But if your kid’s temperature reaches 102 F (38.8 C) or higher, and home treatment doesn’t lower it, you should call your healthcare provider.
Here are steps you should take to get the most accurate temperature reading for each thermometer. Before following these steps, it’s important you also read the instructions that come with each instrument before using them.
Digital oral thermometer instructions
- Wait until 30 minutes after your child has had anything hot or cold to drink.
- Turn the thermometer on and place the tip in the pocket under either side of your child’s tongue.
- Have your child close their lips around the thermometer and hold the thermometer in place with their hands. They shouldn’t bite down on the thermometer.
- Keep their lips sealed until the beep, then remove and read the result.
- Clean the thermometer with a cotton ball moistened with rubbing alcohol and let dry.
Digital rectal thermometer instructions
- Use a small amount of petroleum jelly on the end of your thermometer and on your child’s bottom at the opening of their rectum.
- Place your child either on their back with their legs pulled up to their chest or chest down on your lap or a firm surface, like the floor. Avoid raised surfaces or countertops because of the risk of falling.
- Turn the thermometer on and insert it about 1/2 inch if your baby is less than 6 months old or 1 inch for babies 6 months and older. Hold your child still and leave the thermometer in place until it beeps, then gently remove and check the reading. Many rectal-specific thermometers will have a small ridge near the tip as a reference point to avoid placing the thermometer too deep.
- After rediapering your child and placing them in a safe place, clean the thermometer with a cotton swab moistened with rubbing alcohol, making sure to clean in the crevices.
Digital axillary (armpit) thermometer instructions
- Turn on the thermometer.
- Place the tip of the thermometer in the center of your child’s armpit.
- Hold your child close to you with their arm next to their body. Be sure the tip of the thermometer isn’t visible to you.
- Wait for the beep, remove the thermometer and read the result.
Ear thermometer instructions
- Place the protective cover on the tip of the thermometer.
- Pull their ear back and up to open the ear canal if your child is 6 months to 1 year of age. If your child is over 1 year old, pull gently back on the top of the ear to open their ear canal.
- Gently insert the thermometer until their ear canal is fully sealed off and aim the tip of the thermometer between their opposite eye and ear.
- Press and hold the button for one to two seconds until you hear a beep (or follow the manufacturer’s instructions).
- Remove the thermometer and discard the disposable cover.
Digital forehead thermometer instructions
- Most thermometers will need to be slid or pressed against the temporal artery, which lies just under the skin on either side of the forehead. If it’s a noncontact infrared thermometer, you’ll want to hold the thermometer perpendicular to your child’s forehead.
- Make sure your child’s head is clean and dry without use of any recent hats, headbands, head wraps, cosmetic wipes or facial cleansing products. Excessive sweating can also make the readings inaccurate.
- Before use, the thermometer should be allowed to acclimate for 10 to 30 minutes in a room or environment that is between 60.8 F and 104 F (20 C and 40 C).
- Make sure you take your child’s temperature while standing out of direct sunlight, as this could affect the thermometer’s accuracy.
- After the beep, read the display.
- Clean the head of the thermometer per the manufacturer’s instructions.
“If you’re not sure if you have the right thermometer, talk with your pediatrician or healthcare provider who can point you in the right direction,” says Klein.