Choosing a thermometer

We often rely on our parental instincts to know if our child has a fever. We put our hand on his forehead, examine his eyes or even smell his breath.

Although there are many different types of thermometers, they all have the same function : tell us if our child’s fever has gone up or down. The accurate number of degrees is important, but what really matters when we take our sick child’s temperature repetitively is whether or not the fever is going down. It is therefore important to always take the temperature with the same device. There can be small variations from one thermometer to another, which could be misleading.

The traditional mercury thermometer has been replaced by the more user friendly digital thermometer. It’s often possible to get the temperature in less than fifteen seconds… very useful when you have a fidgety baby! With a mercury thermometer, there’s also a risk of being exposed to toxic substances if it breaks. Mercury is dangerous for the environment and although mercury is a liquid at room temperature, it easily evaporates into a gas that has no smell. That gas, or vapor, is toxic if it is inhaled. The Canadian Paediatric Society no longer recommends the use of mercury thermometers.

Rectal thermometer

For : this thermometer is especially suitable for children aged 0-5 years. With older children, the experience can be unpleasant and embarrassing.

Beware! The Canadian Paediatric Society reminds us that “rectal temperatures are slow to change in relation to changing core temperature, and they have been shown to stay elevated well after the patient’s core temperature has begun to fall, and vice versa. Rectal readings are affected by the depth of a measurement, conditions affecting local blood flow and the presence of stool. Rectal perforation has been described, and without proper sterilization techniques, rectal thermometry has the capacity to spread contaminants that are commonly found in stool."

How to take a rectal temperature:

• Put the child on his stomach. If he is really small, you can place him on your knees.
• Apply petroleum jelly (vaseline) on the tip of the thermometer and on the rectum.
• Gently insert the thermometer in the rectum (about 1 inch). For children younger than 6 months, don’t go deeper than half an inch. Make sure the child moves as little as possible.
• When the thermometer beeps, remove the device gently.

Normal temperature range with this method
From 36.6 °C to 38.0 °C ( 97.9 °F to 100.4 °F)
Source : Canadian Paediatric Society

Axillary thermometer (armpit)

For: children over 2 years old

Beware! While axillary temperature is easy to measure (compared with oral or rectal measurements), it has been found to be an inaccurate estimate of core temperature in children. This type of measurement relies on the thermometer remaining directly in place over the axillary artery, and it is largely influenced by environmental conditions. Despite its low sensitivity and specificity in detecting fever, axillary temperature is recommended by the American Academy of Pediatrics as a screening test for fever in neonates because of the risk of rectal perforation with a rectal thermometer.

How to take an axillary temperature?

• Make sure that the child’s armpit is dry.
• Put the tip of the thermometer under the child’s armpit.
• Keep the thermometer in place by pressing the armpit against the body (by holding the child’s elbow against his chest).
• Be careful not to let air pass under the child’s arm (so that it doesn’t influence the temperature).
• When the thermometer beeps, remove the device gently.

Normal temperature range with this method
From 34.7 °C to 37.3 °C (94.5 °F to 99.1 °F)
Source : Canadian Paediatric Society

Oral thermometer

For : For children older than 5 years, this is the best technique and should become the definitive method from now on.

Beware! When taking your child’s temperature orally, you must first inform him that he will have to keep his mouth completely closed during 3-4 minutes, with his tongue pushed down on the thermometer. It’s no easy task. Consider having him watch television, or read him a book, while he has the thermometer in his mouth to keep his attention and prevent him from getting impatient. Stay with him and distract him without asking questions that would require him to answer you!

The better a child follows directions, the more reliable the reading will be. “However, oral temperature is easily influenced by the recent ingestion of food or drink and mouth breathing. Its accuracy lies somewhere between that of axillary and rectal thermometry”, explains the Canadian Paediatric Society.

How to take an oral temperature?

• Don’t take the child’s temperature if he has eaten either very hot (soup, broth, etc.) or cold (ice cream, yogurt, etc.) foods in the previous 30 minutes.
• Place the tip of the thermometer under the tongue and ask your child to close his lips around it. Remind your child not to bite down or talk, and to relax and breathe normally through the nose.
• When the thermometer beeps, remove the device gently (with a glass thermometer, leave it in the mouth for 3-4 minutes).

Normal temperature range with this method
From 35.5 °C to 37.5 °C (95.9 °F to 99.5 °F)
Source : Canadian Paediatric Society

Tympanic thermometer

For : Children older than 2 years.

Beware! Instead of being in direct contact with the TM, today’s tympanic thermometers measure the thermal radiation emitted from the TM and the ear canal, and have therefore been called infrared radiation emission detectors (IRED). However, the Canadian Paediatric Society recommends continuing to take the temperature of children under two years rectally until a suitable cap is fabricated for tympanic thermometers.

And don’t worry: earwax, ear infections and ear tubes, however, do not interfere with accurate readings.

How to take a tympanic temperature?

• If the child was outdoors on a cold or windy day, it is recommended to wait 15 minutes (indoors!) before taking his temperature.
• An accurate temperature depends on pulling the ear backward to straighten the ear canal.
• Insert the tip of the thermometer in the ear and press on the button. You’ll have the temperature within a few seconds.

Normal temperature range with this method
From 35.8 °C to 38.0 °C (96.4 °F to 100.4 °F)
Source : Canadian Paediatric Society

Hygiene

Remember to wash and sanitize the thermometer after each use, otherwise the risk of spreading germs multiplies. Always wash the thermometer before storing it in a safe place. It’s a fragile object that must be handled with care.

Choosing a thermometer

The choice is up to parents. First, rely on the method you must use with your child, according to his age. The choice can then be influenced by several factors. For an informed choice, just ask your pharmacist for advice. He will explain the advantages and disadvantages of all models:

• Convenience (size, weight, style, etc.)
• Possibility to take the temperature in more than one location (rectum, armpit and mouth) rather than an ear thermometer.
• Casing
• Response time
• Accuracy
• The safety of the infrared tympanic thermometer
• Audio signal when the reading is done
• Indicator for rectal insertion
• Results shown in Fahrenheit or Celsius
• Product strength

For their user-friendly aspect, mothers often prefer to use ear thermometers. Their practicality is undeniable: you can take the child's temperature when he’s sleeping without disturbing him. No need to wake him up! A sick child is already not very cooperative, so let’s not complicate things. After all, the important thing is to be able to determine whether the child has a fever or not, and then whether it goes up or down. You’re not doing a statistical study!

What about you? How do you proceed at home? Email us.

Sources : University of Michigan Health System and Canadian Paediatric Society.