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Taking your child’s temperature: what’s safe and what’s not?

By Hannah Fox

Unsure what's a safe temperature for your baby or child? We’ve got expert advice on that, plus tips on how to use a thermometer accurately.

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Babies and children can be magnets for all the bugs that are doing the rounds at nursery and school. At times it may feel like you’re going from one round of runny noses and temperatures to another, so it's vital that you're able to spot when your child is running a fever, monitor it accurately, and recognise if it’s got too high.

We’ve asked an expert paediatrician for tips on what to look out for, and the safe temperature window for a baby or child.

We’ve also reviewed a range of digital thermometers, looking at functionality, convenience and different features. Read our first look reviews of digital thermometers.

Spot the first signs of a temperature

If your baby or child seems a little under the weather, it’s worth checking if he or she has a temperature. Typical signs to look out for include:

  • hotter-than-normal forehead, back or stomach
  • skin and head feeling sweaty
  • flushed cheeks.

More serious signs of illness (such as sepsis) that might accompany a temperature include:

  • pale skin, lips or tongue
  • not responding to social cues
  • decreased activity
  • waking only with prolonged stimulation
  • breathing difficulty
  • dry mouth or no tears
  • poor feeding in infants
  • producing less urine.

How to take your baby’s temperature

‘When taking their temperature orally, make sure it’s not been within 30 minutes of the child eating or drinking hot or cold food,’ says Dr Donald Macgregor, a consultant paediatrician, senior lecturer in child health, and spokesperson for the Royal College of Paediatrics and Child Health. ‘Wait 15 minutes before measuring ear temperature if your baby has been outside on a cold day.’

Some of the most popular digital thermometers are infrared tympanic thermometers (ear thermometers), but you can also get digital oral thermometers (old-fashioned mercury ones are no longer recommended), and infrared ‘no touch’ thermometers which you use on a person’s forehead.

‘Strip thermometers, which you stick directly on to a child’s forehead, are not accurate and should be avoided,’ Dr Macgregor says. ‘Placing a digital thermometer under the armpit is not a very good place for parents or carers to measure temperature accurately, as you need to leave it there for several minutes. This could be tricky with a wriggly baby, although it is still used in hospital for newborns.’

Each type of thermometer will work in a different way, and you should always check the device's instructions before taking your first reading. For example, when using an infrared forehead thermometer you’ll need to ensure that you push hair back from the face, and you may need to dab away any perspiration. With an ear thermometer, you need to insert it at the correct angle to ensure you get an accurate reading.

What is a safe temperature range for a baby or child?

While there’s a fair bit of variation with kids, the normal range for children is 35.8°C to 38°C, with it usually falling around 36.4°C. However, it’s worth taking your baby’s temperature when they’re well a few times so you get an idea of what’s normal for them.

‘If your baby is under three months and has a temperature of 38°C, that’s considered a fever,’ Dr Macgregor says. ‘In this case, we’d recommend you take your baby to a doctor, regardless of whether he or she has any other symptoms of illness.’  

Any child aged three to six months with a temperature of 39°C or higher, or six months and over and with a temperature of 40°C, should be assessed by a clinician.

What causes a high temperature in a baby or child?

A high temperature or fever is often in response to a viral or bacterial infection in the body. In fact, it’s the body’s way of fighting it off, which is why doctors often recommend you try to avoid giving Calpol unless your child is distressed by the fever or until after you’ve seen a doctor.

‘High temperature and fever can also happen after immunisations, allergic reactions, inflammatory conditions and severe dehydration or sunstroke,’ says Dr Macgregor. ‘There’s no science to suggest teething causes fever.’

What should you do if your baby or child has a temperature?

If you see any of the symptoms mentioned above in your baby or child, and they have a high temperature, it’s worth contacting your doctor.

‘However, it’s best to hold off giving any baby paracetamol such as Calpol until after the health professional has assessed them,’ Dr Macgregor advises.

If you need to speak to someone outside of normal surgery hours, call your GP’s out-of-hours service or NHS 111.

‘Sometimes parents get so worried about their child having a fever, and seeing that as the sign of illness (when in fact it’s the body fighting the illness), that they give infant paracetamol or ibuprofen when it’s not needed,’ Dr Macgregor says.

It’s been dubbed ‘fever phobia’, and many expert paediatricians have warned against routinely giving Calpol and other fever-reducing medicines (known as antipyretics) unless their child is in clear distress.

‘If your child is running a temperature, but generally feeling OK, they should be treated with rest and fluids,’ Dr Macgregor says.

If the fever continues for more than five days, you should contact your GP for your child to be assessed again.

Febrile convulsions

These are a type of fit (seizure) that can happen when a child has a high temperature, although it’s not thought that the fever itself causes the convulsions. While they can be scary for parents to watch, in most cases they are not harmful to your child.

They usually last about five minutes. Your child will become stiff, their legs and arms may twitch, and they may lose consciousness and wet or soil themselves. Your child may be sleepy after the seizure.

If your child has a febrile convulsion, you should stay with them, and try to put them in the recovery position. Make a note of how long the seizure lasts. If this is the first fit they’ve had, or it lasts longer than five minutes, call emergency services on 999.

Calpol or other infant pain relief will have no effect on preventing febrile convulsions.

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