With cold and flu season about to kick off and kids back at school and life trying to resume, amid the COVID-19 pandemic evolution, it is highly likely that at some point, you will be reaching for your family thermometer. More than ever, you want it to be accurate.  

Temperature accuracy is a crucial and time critical measurement in identifying any signs of illness or deterioration. So, as soon as your child starts complaining of low energy or if they feel a bit warm, you should immediately start measuring their body temperature.

Checking your body’s temperature with a thermometer is an easy way to see if a fever is present. Fever is a condition that goes with an abnormal raise of body’s temperature and is usually caused by an infection. It is a sign that the body is fighting off that infection.

Body temperature varies over the course of the day and varies among individuals – with women tending to have higher body temperatures than men, and younger people tending to have higher temperatures than older ones, with temperature being lowest in the morning and highest in the evening.
So, what kind of thermometer should you use to get the most accurate result, how should it be used and how to interpret the readings to know what temperature constitutes a fever?

Thermometers: understanding the options

There are many different types of thermometers you can use to measure temperature. When you are taking the temperature of your child, the ideal thermometer should be non-invasive, easy to use and it should give an accurate, consistent and relevant reading. Let’s see what are the options and what are their pros and cons.
First of all, please be aware that in most parts of the world the old mercury-based thermometer is no longer in use and selling them is forbidden. They can easily break, and their fluid is toxic. Do not use them.

Generic digital thermometers
Digital thermometers use an electronic heat sensor to record the body temperature. They can measure the temperature at the skin level and are used in “closed” areas (armpit or groin) to ensure a proper contact and isolation from the environment. Skin is a thermoregulating organ that interacts with the ambience to regulate the inner (central) temperature, so it can have significant temperature differences with the central values. Applying the thermometer and keeping it sable in place are challenges that preclude a consistent reading.
This is why temperature is preferably measured with this technology in natural orifices that can approach the reading to the central temperature, either in the rectal space or the mouth.
This procedure remains the most frequently used because of their respective advantages but they are not free from challenges:
Rectal thermometers are obviously a bit threatening especially to children, the most frequently patient group for this method, but it is a highly accurate and relevant, remaining the standard of care for non-invasive measurement of the central temperature, even if there is also a time lag between central temperature (measured invasively) and the temperature in the rectal vault.
Rectal temperature is contraindicated in patients with neutropenia (low or suppressed immunity).
Oral temperature is highly influenced by the stability of the thermometer in the right sub-lingual spot; patient’s ability to keep the probe stable in place and properly isolated is not easy and the readings can show significant user-dependent variability.
A rapid respiration (tachypnoea), having recently taken cold or warm liquids will add difficulty for a proper measurement. On the other hand, oral temperature takes time before a central hight temperature manifests itself in the mouth, so it is highly recommended to take a series of measurements over more than one hour on the suspicion of a fever.
Needless to say, when applied to either mouth or rectum the probe should be covered with a single use cap, most hygienic but with cost and waste implications.
When used in the skin the probe should be cleaned and sanitized with the same care applied to other multi-use clinical tools like a stethoscope or a dermatoscope.

Digital ear or tympanic thermometers
In-ear thermometers are fast, accurate and closer to central temperature than armpit or groin measurements. The main drawbacks are that they can be painful if not done properly and for a consistent and patient-comfortable reading they require a good technique to be performed. They might not be usable if a child has a cold with a non-infrequent otologic involvement and are not suitable for new-borns.
Anatomical variations of the outer ear channel and presence of wax can add challenges to obtain a proper reading.
Even if the outer ear channel is covered with skin, these thermometers should be used with sterile caps with the same cost and waste implications as the rectal and oral temperature case.

Temporal artery thermometer
Temporal artery thermometry reads the central temperature by capturing the arterial blood temperature at the temporal level, were the anatomical setting is most reproducible across ages and body sizes and compositions.
Scanning the forehead over the temporal artery with a temporal artery thermometer is fast and very accurate. This type of thermometer is also not invasive or threatening to children or adults because the actual measurement is done by swiping the thermometer gently touching across the forehead of the patient. The technique can be performed within 2 seconds without disturbing a resting patient.
There are 2 challenges that can easily be overcome: 1) the measurement technique and 2) the sweating patient, that requires a special technique to complete the temperature reading properly.
This technology is only applied to the skin, which gives the opportunity to keep a clinical grade hygiene without the use of single use caps, reducing cost and waste.
In special clinical settings where an extra caution is advised (isolated immunosuppressed patients for instance), there are sterile caps that can be applied either for individual or for single use.
In summary, the pros of temporal artery thermometers are:

  • fast
  • easy
  • cost-effective
  • comfortable and sleep non-disturbing for all, children, teens and adults
  • highly predictive of fever as measured by rectal thermometry (1)

What is a normal body temperature?
Normal central body temperature is 98.6 degrees Fahrenheit (°F) or 37 degrees Celsius (°C). Normal temperature often varies from 1° to 2°F (½° to 1°C). A normal temperature is usually lower in the morning and increases during the day. It reaches its high in the late afternoon or evening.

What temperature is considered a fever?
As the thermometry depends on the method used, the general cut-off value for fever is:

  • measured orally (in the mouth): 100°F (37.8°C)
  • measured rectally (in the bottom): 100.4°F (38°C)*
  • measured in an axillary position (under the arm): 99°F (37.2°C)
  • measured with temporal artery thermometry: 100.4°F (38°C)*

*Central temperature

When should you call a doctor when a person has a fever?
In general, if the central temperature is 102°F (38.8°C) or higher and if fever is present for over 2 days but, along with temperature, you should seek for signs that can help you take the decision. Here is some advice:

  • 0 – 3 months – if the body temperature is 38°C or 100.4°F or higher
  • 3 – 6 months – if the body temperature is 39°C or 102°F or the child is unusually irritable, lethargic or uncomfortable
  • 6 – 24 months – if the body temperature is higher than 39°C or 102°F and the fever lasts longer than one day but the infant shows no other symptoms.


  • 24 months if the body temperature reaches 39°C or 102°F

As per the NICE guidance, by observing the activity of an infant you can assess the level of severity and seek for medical care (2)
Green represents a low risk, yellow a moderate risk (seek for help) and red a high risk (seek for help immediately)

Activity – Table 1. Excerpt from the NICE: Traffic light system for identifying risk of serious feverish illness.


  • Responds normally to social cues*
  • Content/smiles
  • Stays awake or awakens quickly
  • Strong normal cry/not crying


  • Not responding normally to social cues*
  • No smile
  • Wakes only with prolonged stimulation
  • Decreased activity


  • No response to social cues
  • Appears ill to a healthcare professional
  • Does not wake or if roused does not stay awake
  • Weak, high pitched or continuous cry

* A child’s response to social interaction with a parent or healthcare professional, such as response to their name, smiling and or/giggling.

If the body temperature is 39°C or 102°F or higher, if it lasts more than 2 days or if
the person shows warning signs like (3):

  • A change in mental function, such as confusion
  • A headache, stiff neck, or both
  • Flat, small, purplish red spots on the skin (petechiae), which indicate bleeding under the skin
  • Low blood pressure
  • Rapid heart rate or rapid breathing
  • Shortness of breath (dyspnea)
  • A temperature that is higher than 104° F (40° C) or lower than 95° F (35° C)
  • Recent use of drugs that suppress the immune system (immunosuppressants)

Fever amid the COVID-19 pandemic.
Fever is one of the most common signs of COVID-19. Cough and tiredness are the other two, but they can be mild in the early phases, hidden behind the common life circumstances and easily underestimated. Fever is a sign (something objective), not a symptom (something subjective); hence, measuring temperature is key for an early diagnosis and therapy, plus the effective contention of the infectious spread.
As per the WHO guidance, “If you have minor symptoms, such as a slight cough or a mild fever, there is generally no need to seek medical care. Stay at home, self-isolate and monitor your symptoms. Follow national guidance on self-isolation.
Seek immediate medical care if you have difficulty breathing or pain/pressure in the chest. If possible, call your health care provider in advance, so he/she can direct you to the right health facility.”
The WHO recommendations to protect ourselves and other are:
“Practicing hand and respiratory hygiene is important at ALL times and is the best way to protect others and yourself.
When possible maintain at least a 1 meter distance between yourself and others.
This is especially important if you are standing by someone who is coughing or sneezing.  Since some infected persons may not yet be exhibiting symptoms or their symptoms may be mild, maintaining a physical distance with everyone is a good idea if you are in an area where COVID-19 is circulating.” (4)

Keeping social distance and observing the hygienic protocols is difficult for everyone in general, but with children in particular is even more challenging. We all know that school is a breeding ground for germs and getting sick is all part of the process of building up a strong immune system.
This is why we need to intensify our efforts to educate them in three behaviour (starting by our example!):
Wash hands often with water and soap and use a hand sanitizer meanwhile.
Show them how to cover their mouth and nose when coughing or sneezing and avoid touching eyes, nose and mouth if their hands are not clean.
Of course, avoiding close contact with anyone who is sick and with the people at risk.
By following these measures and measuring temperature frequently as frequently as needed, you can keep your children, your family and yourself safe during flu season and beyond.
We believe that Exergen’s Temporal artery thermometer represents the most accurate, easiest to use, safest and most cost-effective thermometry solution from the hospital setting to our homes.