Everything you need to know about thermometers in 2021

A digital thermometer.

All of us get sick from time to time, with fever from a cold, flu, or other diseases like the recent Covid-19-pandemie that might bother us. Especially families with children need a reliable clinical thermometer, as children often get sick. Many parents have a hard time choosing, as thermometers come in various designs and functions: analog or digital, contact or infrared, for measuring on the forehead, ear or temple, non-contact or not. We would like to provide you with a helpful overview to find the most suitable thermometer for you and your family. 

A thermometer with medicine. These days most devices are digital.
A thermometer with medicine. These days most devices are digital.

Nowadays, some thermometers measure both in the ear and on the forehead, some only on the forehead and others only in the ear. Besides, there are regular contact clinical thermometers. Some thermometers can also measure the surface temperature of objects and liquids and the room temperature.

New generation thermometers: Forehead or ear measurement: Which is better?

Until just a few years ago, there wasn’t much choice when choosing a clinical thermometer. Every family had a simple glass mercury thermometer at home.

Today, they are all but extinct. There are several reasons for this: First, reading the temperature on an analog thermometer is not very easy, and second, glass is not safe to handle with small children, especially if it contains a highly toxic substance like mercury. In the EU, the sale of measuring devices filled with mercury has therefore been banned since 2009.

Classic analog and digital contact clinical thermometers

Classic analog clinical thermometers made of glass are still available for purchase today, but they contain a different non-toxic measuring liquid.

In digital clinical thermometers, the temperature is recorded via a sensor located in the thermometer’s tip. The conductivity in the sensor changes as soon as the temperature changes. This change is shown on display as a temperature value.

A touchless digital thermometer.
A touchless digital thermometer.

These so-called contact thermometers measure very accurately, and you can get them for a few dollars or euros in the drugstore or online. You don’t have to spend more than ca. 10 USD or 10 euros on them.

Digital thermometers are more accurate but take longer to measure the temperature. However, from a certain age onwards, most children will only allow themselves to be measured rectally under great protest or not at all. And even babies don’t want to be undressed each time you want to determine whether the baby has another cold.

However, measuring with analog and digital contact thermometers takes a relatively long time. And even holding still for one or two minutes can be a challenge for both child and parent when taking a temperature.

Infrared clinical thermometers

Infrared clinical thermometers measure the infrared radiation emitted by the body. It is transmitted through a lens to the thermometer’s sensor and converted into a temperature value that appears on display.

Infrared clinical thermometers are therefore a real blessing, especially for children. They measure the body temperature within seconds and do not provoke any screaming – exactly what parents want.

The advantage over conventional contact thermometers is that a measurement result is available after just a few seconds. 

Infrared thermometers nowadays also measure very accurately.

In principle, infrared thermometers can now measure with similar accuracy to analog or digital contact clinical thermometers. The measurement in the buttocks is still the most reliable because it is measured inside the body. This is not only the closest to the body’s core temperature; it is also the area where the measured value is least likely to be falsified by interfering influences.

An infrared thermometer, on the other hand, measures either on the forehead or in the ear. Whereas the rectal measurement is an exact reflection of the body temperature, the temperature on the forehead or in the ear can give false results, such as if a cold is coming up.

Suppose you have a high fever and you want to know exactly the temperature. In that case, there is still no alternative to rectal measurement in the buttocks with a contact clinical thermometer. Therefore, everyone should also have a simple, digital tools for rectal fever measurement in the house.

But in many cases, ear or forehead measurement with infrared is sufficient. After all, you often just want to determine if you or your child have a fever or if the body-temperature has changed. Therefore, you don’t always have to “torture” your child with a rectal measurement.

There are two different measuring methods for infrared: on the forehead or in the ear. Both have their advantages and disadvantages.

Different fever thresholds

It is important to note that different temperatures are measured at all measuring points, whether forehead, ear, mouth, armpit, or buttocks. Accordingly, the fever threshold is also different depending on the body part. If measured rectally, a temperature of 38.0°C or higher is considered a fever. In the ear, the threshold is 37.7°C, under the armpit and in the mouth 37.2°C, and on the forehead 37.4°C. Just remember that when you are exercising your body temperature may rise a bit.

Different body sites give different readings.

The good news is that you don’t have to remember the different temperatures. Most infrared thermometers for measuring on the forehead or in the ear indicate this area’s temperature reliably. Most use a color code for this: green means “everything is fine,” orange means “increased temperature,” and red means “fever.” Some tools also allow you to specify the patient’s age, in which case the fever thresholds are adjusted accordingly. Some also work with health apps, so you can remotely update your health status.

The fever threshold for babies is 38.5°C, which is slightly higher than for adults. 

But be careful: The fever threshold is higher in babies and toddlers than in adults! Babies have a normal body temperature between 36.5°C and 37.5°C. Between 37.6°C and 38.5°C means an elevated temperature, and from 38.5°C on, a baby is said to have a fever. Especially for newborns and babies a few months old, you should consult a doctor if the temperature reaches 38.5°C because fever can quickly become dangerous for babies. 

Ear measurement

For some time now, pediatricians have measured fever only in the ear from the age of two. On the one hand, this is quick and uncomplicated for everyone involved, and on the other hand, the accuracy of the measurement is hardly inferior to that of conventional thermometers.

However, it is essential to measure both ears and take the higher value when measuring in the ear because this is the decisive one.

The ear measurement is not quite simple. You have to aim the sensor precisely at the eardrum. To do this accurately, the ear must first be pulled into the correct position to stretch the curved auditory canal. In the case of small children, you have to pull differently from older children and adults.

If you do not hit the eardrum but the ear canal’s wall, the temperature is about 1 degree too low. A lot of earwax can also falsify the measurement result. And in the case of otitis media, no ear measurement should be carried out at all.

There is also the issue of hygiene: contact with skin and earwax can transmit pathogens. Therefore, some ear devices require a protective cap to be put on for each measurement, which is then disposed of. This is inconvenient and causes costs and waste.

Forehead measurement

Forehead thermometers are not yet as established as ear alternatives, but they are gaining ground. The reason: children and babies usually do not find the measurement in the ear particularly pleasant. With the forehead device, you simply move along the forehead and have a result in seconds.

Some devices even work without contact so that even a sleeping child can be measured for fever. Hygiene should not be forgotten; as with contactless measurement, no pathogens can be transmitted via the device.

To quickly check whether the child has a fever or whether the temperature has changed, the forehead measurement, therefore, makes the most sense in our view – but only as a supplement to the precise rectal control measurement with a contact tool. But this is also necessary with the ear measurement.

However, the forehead measurement is most prone to error. If the child were lying with his forehead on the pillow or directly under a lamp, it would show a much too high temperature.

If the measured values seem strange to you, please do not be alarmed at first, but repeat the measurement a few minutes later – or measure rectally with the contact thermometer.

There are also combination devices available with both forehead and ear measurements. 

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Philippa White

Author: Philippa White

Philippa worked as a copywriter in Asia and Australia for several magazines and newspapers. She has extensive knowledge in health and lifestyle and is still active as a part-time Yoga instructor.

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