Thermometers and body temperature: experts answer urgent questions


Although not everyone with COVID-19 can develop a fever, it is still one of the most common symptoms associated with the new coronavirus.

You can easily check your body temperature using a thermometer; experts even recommend keeping one in your medicine cabinet to watch for this telltale sign of the virus. But with so many different types of thermometers, it can be difficult to determine which one is best for you.

According to Natalie Crown, pharmacist at Women’s College Hospital and assistant professor of education at the University of Toronto’s Faculty of Pharmacy, finding the right thermometer comes down to two things:

“The two main considerations are that you want accurate measurement … and ease of use,” Crown told by phone on Monday.

These factors guide many of the recommendations made by health professionals and associations about which thermometers are best suited for adults and children of different ages, she said. spoke to the Crown and Dr. Matthew Oughton, infectious disease specialist and assistant professor in the department of medicine at McGill University, about some frequently asked questions about thermometers and how to use them.


The US Centers for Disease Control and Prevention (CDC) considers a fever to be “a measured temperature of 100.4 degrees Fahrenheit [38 C] or larger. That said, the institute of public health also recognizes that this figure can vary depending on the type of thermometer used and the age of the person being tested. Generally, he defines fever as a temperature “high above [a person’s] standard. “

There is much debate surrounding what is considered “normal” body temperature for humans. While Harvard Medical School points out that this figure has long been considered to be around 37 C, or 98.6 F, new research suggests that it could be an overestimate, and that the average body temperature for humans today hui is actually about 36.4 C or 97.5 F.

Oughton also explains that a number of factors can affect a person’s body temperature, including the time of day.

“On average, most people’s core temperatures tend to be a bit lower in the morning around 6 a.m. and a bit higher in the evening, around 6 p.m.,” Oughton told on Monday. phone. “This normal variation can reach up to half a degree Celsius. “

But despite all of these contributing factors, as well as the debate over what is considered “normal,” Oughton said that the CDC’s definition of fever is the standard he recommends following.

“On average, a temperature of 38 [C] is unquestionably a fever, “said Oughton. “I don’t think a doctor can really quibble with 38 [C] as a reasonable indicator [of fever]. “


According to Crown, not all thermometers are likely to offer the same temperature reading, even when used on the same person.

“Normal body temperature depends somewhat on where you measure your temperature,” she said.

The main different types of thermometers are rectal, oral (mouth), tympanic (ear), axillary (armpit) and temporal (forehead). Since different parts of the body maintain slightly different temperatures, readings from thermometers used in the mouth, forehead, and ear, for example, are not likely to produce exactly the same results. Oughton explains that rectal thermometers are considered the most accurate when measuring a person’s body temperature.

“We generally think that the rectal temperature is the one that best reflects the true central body temperature,” he said.

This is due to the fact that he is able to get the best reading from inside the body. Ear thermometers are also considered to offer a similar level of accuracy when taking temperature.

Aside from these parts of the body, others often examined for temperature measurement offer slightly different results. According to a medical examination by Healthwise, a nonprofit organization specializing in health education, a person’s oral temperature is generally 0.5 ° C lower than that of their rectal or ear temperature. In addition, a person’s armpit and forehead temperatures are generally 0.5 ° C below their oral temperature.

Oughton points out that it’s important to keep this in mind when taking your temperature to determine if you have a fever.



For the average family with no special needs, Oughton said he would most recommend a digital mouth thermometer.

“It’s probably the most useful overall and the best cost balance [and] benefits, “he said.

While waiting times for results can range from a few seconds to about a minute, many have the option of beeping or offering another signal to show that reading is complete, making it easier to use. These thermometers are also available with flexible or rigid tips, depending on the preferred style.

The Crown recommends that families keep a digital thermometer with them at home.

“It has the advantage of being able to be used in three ways – you can use it under your tongue … for older children and adults,” she said. “You can also use it in young children, under the arm to take a measurement under the armpits or rectally. “


The next best option, said Oughton, would be a forehead thermometer. They’re incredibly easy to use and one of the most comfortable thermometers available. Through the use of an infrared scanner, these devices measure the temperature of the temporal artery of the forehead.

Front thermometers, like many other infrared thermometers, read the temperature fairly quickly, usually within seconds. Many also come with a function to signal that the reading is finished, like a beep. According to the Mayo Clinic, these thermometers should not be used on infants less than three months old.

” In [older] children and adults, temporal artery [forehead] thermometers may well be the second most accurate measurement tool that reflects the true core body temperature, ”said Oughton.

There is one major drawback – the price. Front thermometers are often more expensive than their digital counterparts.


Another slightly less expensive recommendation is the digital ear thermometer. These devices also measure temperature using an infrared ray, but inside the ear canal. They are generally quick to record temperatures and comfortable enough for children and adults.

According to the Mayo Clinic, digital ear thermometers are only recommended for infants over six months of age as well as children and adults.

Oughton advises people to be wary of any existing earwax when using these thermometers, as this can affect the accuracy of the results. He also recommends that people avoid taking their temperature with digital ear thermometers if they come from the inside out.

“Don’t measure the temperature right away, because you can get a falsely low temperature, which is exactly the wrong thing if you’re trying to get a fever,” he said.

He suggests waiting about 10 minutes for the temperature in the ear canal to balance with your surroundings before taking your temperature with this thermometer.


For infants, Oughton said he would recommend rectal thermometers for the most accurate reading. He also advises families to clearly label the thermometers they plan to use rectally and store them in their own compartment.

Crown also recommends the use of underarm thermometers for children. While she recognizes that rectal thermometers provide more accurate reflection of body temperature, a digital thermometer placed directly in the middle of a child’s armpits is also a good option.

“In children, the most accurate way to take a temperature is to take a rectal measurement, but we know it is difficult to do,” she said. “For most young children – babies and children up to the age of five – using a sleeve thermometer under the armpit is actually a very effective way of taking a child’s temperature. “


In addition to having a working home thermometer and perhaps keeping a few extra batteries, Oughton also recommends eating nothing before taking his temperature. Having something particularly hot or cold to eat or drink, for example, could have an impact on your temperature reading, depending on the thermometer used.

“You are not supposed to have anything in your mouth for about 15 minutes before checking your temperature if you want it to be as accurate as possible,” he said.

It also reminds people to make sure they cover the entire sensor or thermometer bulb, depending on the type used, each time they take their temperature to ensure the most accurate reading.

Finally, Crown advises contacting your local pharmacist if you have any specific questions you may have about thermometers, including what type you should use and how to use it.

“We recognize that choosing a thermometer can sometimes be confusing,” she said. “Pharmacists are the most accessible health care provider and are available to advise families on how to interpret the temperatures they are getting, and then to provide advice on how to treat fevers.

“I would recommend going to your local pharmacy or even calling them at times like these, where we all try to stay at home. “


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