"Mummy, I feel sick!" A cry that's all too familiar to most parents. A hand on your child's forehead is a good first step when checking for fever, but for a proper measurement you'll need a thermometer.
You have several options when choosing a thermometer; you won't find old mercury or alcohol models on most retail shelves these days.
Digital probe thermometers are accurate and cheap.
Used for oral, armpit or rectal readings, these are the most commonly available type of thermometer. Features vary depending on what you pay for, but can include a fever alert indicator, large display and a recall of the last reading.
- Accurate for oral and rectal readings, often up to 0.1°C
- Relatively cheap.
- Some can give oral results in as little as 8-10 seconds.
- May take up to two or three minutes for some models to give a result for armpit (axillary) readings, so may not be suitable for restless babies or children.
Ear thermometers are quick but must be positioned correctly.
These are inserted into the ear canal and use infra-red rays to read the core body temperature.
- Less invasive than digital probe thermometers.
- While a good ear thermometer can be accurate, they must be carefully positioned to get an accurate reading. That may be hard if the thermometer is not shaped to suit the eardrum, or if your child's ear canal is too small.
- Either ear may show a different reading, and there must not be any built-up earwax.
- Not generally recommended for infants under six months.
Forehead thermometers are non-invasive but results can vary.
These use an infrared scanner to measure the temperature of the temporal artery in the forehead.
- Quick (one to three seconds for a result)
- Some are "touchless"; these are handy for a sleeping infant and can limit the spread of germs.
- A good indicator of temperature, but generally not as accurate as a digital probe thermometer.
- Temperature variations may appear depending on skin type, skin colour, whether the subject is wearing make-up, or sweat.
- Aren't always easy to use.
- Aren't usually considered accurate for use on infants under three months.
Some thermometers combine multiple functions.
A plastic strip with heat-sensitive crystals that change colour to give a temperature reading; very easy to use, but not very accurate. Cost around $10 or less.
These contain mercury (a silvery-grey liquid metal) or alcohol (usually coloured red). They are cheap and accurate, but nowadays more likely to be found in an old first aid kit than on a chemist's shelves. They are harder to read than digital thermometers, and there's a risk of poisoning if they break and release their contents.
Nurofen FeverSmart thermometer
This doesn't fit into any other category. It uses a Bluetooth-enabled temperature monitor that sticks under your baby's armpit with an adhesive patch. It connects to an app to continually track your baby's temperature but at $140 plus $10 for a 4-pack of single-use adhesives, it doesn't come cheap.
Some thermometers have multiple functions such as both ear and forehead functionality, or both forehead and touchless modes.
Regardless of which type you choose, always read the instructions to ensure you know how to use the thermometer correctly and get the most accurate reading.
For instance, it's a good idea not to consume anything for half an hour before using an oral thermometer, in case hot/cold foods influence the reading. Similarly, exerting yourself may mean that sweat can influence the accuracy of a forehead thermometer.
If you're unsure, get your doctor to show you the best way to use the thermometer.
Rather than wait until someone is sick until you use your thermometer for the first time, you can find out what constitutes a "normal" temperature for you or your child by noting down multiple readings when you're healthy.
Some ear and forehead thermometers use an algorithm to convert the temperature to an oral temperature equivalent, while others may display a slightly higher "core" temperature. It isn't always clarified in the instructions. Your baseline might also be different depending on other variables such as gender, age, skin type, skin colour, and the ambient temperature.
CHOICE has confirmed that good digital probe thermometers can meet their claimed accuracy to within 0.1°C.
Ear and forehead thermometers are accurate enough, though they usually don't claim to be quite as accurate as digital probes; accuracy to within 0.2°C is the typical claim. Correct usage is the key to getting an accurate reading – read the instructions or get a medical expert's advice.
Time to reading
Probe models generally deliver a reading in less than 60 seconds. Most models wait until the thermometer reaches a stable temperature then emit a tone and display the reading, but some use a predictive method, meaning they take a partial reading and calculate the final temperature based on mathematical modelling. This makes them faster than most other models, and according to CHOICE tests, just as accurate.
Infrared ear and forehead thermometers usually give a very fast reading, often within three seconds or less, making them easier to use on a restless child. The Nurofen FeverSmart takes eight minutes to 'warm' up.
The larger the display, the easier it is to read. Ideally it should be backlit, too, so you can take a reading at night.
Audible beeps indicate when the thermometer is ready to take a reading, and when it has finished. (However, you may not want to be able to turn this off to avoid waking a sleeping child!)
Some models have a tone or colour-coded display to show when the patient's temperature is above normal.
This is useful for comfort, particularly when taking rectal temperatures.
For protecting the thermometer when it's not in use.
Many models can recall at least one previous reading, some as many as 35. This is good to detect whether temperature is improving or stabilising.
For a digital probe thermometer, disposable sheaths help keep the thermometer clean and hygienic – useful if you have to take readings from more than one person, though wiping the probe with sterilising alcohol between readings will also do the trick. Ear thermometers also have compatible, dispoable covers, which are typically required to be in place before they can be used.
It's important that you, the adult user, can easily access and change the battery when needed, but you don't want your child to do that. Many digital probe and infrared thermometers use button batteries, which are very dangerous if swallowed. There's a new voluntary Safety Code for button batteries, and we hope manufacturers will use it to make their products safer. But for small devices such as thermometers, these batteries are likely to be needed for the foreseeable future. So always keep thermometers and any spare batteries well out of reach of young children and don't let them use thermometers unsupervised.