Your child’s average body temperature is about 37°C. If your child’s temperature is higher than 38°C for 24 hours or more, she probably has a fever. A fever is a sign of illness.
Fever is not an illness in itself, but is the sign of an illness. Children get fevers for all kinds of reasons. Most fevers, and the illnesses that cause them, last only a few days. But sometimes a fever will last much longer, and might be the sign of an underlying chronic or long-term illness or disease.
Infections are by far the most common cause of fever in children. Most of these are caused by viruses, which are responsible for colds, upper respiratory infections, and the common infectious diseases of childhood, such as chickenpox. These infections don’t last long and usually don’t need to be treated.
In general, fever is nature’s response to infection, and can actually help the body fight infection.
Some infections are caused by bacteria, and need treatment with antibiotics. These include certain ear and throat infections, urinary tract infections, pneumonia, blood infections and meningitis. For example, a very sore throat with a fever can be caused by streptococcus. If it isn’t treated with antibiotics, this infection can lead to rheumatic fever or heart damage.
There are other, relatively uncommon, causes of fever. These include allergic reactions to drugs or vaccines, chronic joint inflammation, some tumours and gastrointestinal diseases.
During the course of each day, body temperature goes up and down by a degree or two. It’s usually lowest in the early hours of the morning, and highest in the late afternoon and early evening.
A fever might come on slowly and rise over a few days, or it might rise very quickly. The height of a fever, and how quickly it comes on, usually doesn’t have anything to do with the illness that causes it.
Fever in itself is rarely harmful. But the high temperature might make your child feel uncomfortable – he might have chills or shivering when his temperature is rising, and might sweat when it’s falling. Sometimes he might become mildly dehydrated if he’s losing a lot of fluid from the fever and not replacing it.
Febrile convulsions are seizures that happen because of fever. They occur in about 4% of children between the ages of six months and five years. Children outgrow febrile convulsions by the age of 4-5 years. Febrile convulsions have no long-term consequences, but talk to your doctor about them.
Sometimes your child might appear flushed, and her skin might feel warm, but her core (inner body) temperature will be quite normal. This can happen when your child has a cold or has engaged in vigorous physical exercise. It can also happen on a very hot day.
When to see your doctor
Seek medical attention if your child:
- looks sicker than before (more pale, lethargic and weak)
- has trouble breathing
- becomes drowsy
- refuses to drink, and is weeing less often (if your baby has fewer than half the usual number of wet nappies, see a doctor)
- complains of a stiff neck, persistent headache or light hurting his eyes
- vomits persistently, or has frequent bouts of diarrhoea
- doesn’t improve in 48 hours
- is aged less than 12 months and has a fever
- suffers pain
- has a fever above 40°C
- is causing you to worry for any other reason.
A fever will run its course regardless of treatment. Fever is one of the ways the body fights infection. Your child’s temperature will return to normal when the infection or other cause of the fever has completely gone.
In children under 12 months, fever might be a sign of a more significant illness, and you do need to seek medical advice.
Babies under three months of age who develop a fever must be seen by a doctor immediately, because it’s harder to tell if they have a serious underlying illness.
In older children, treat the fever only if you feel it’s making your child uncomfortable, irritable or so lethargic she’s not drinking enough fluids.
Generally, children handle fever well. If your child has a fever, here are some ways that you can make him more comfortable:
- Dress him in light clothing.
- Give him small quantities of clear fluids such as water, weak tea or diluted soda water, lemonade or juice to drink. (Lemonade and juice are too strong for a child with gastroenteritis with diarrhoea – they must be diluted.) Do this often. If your child isn’t hungry, that’s OK. The most important thing is to make sure he’s drinking enough to avoid dehydration.
- Give liquid paracetamol in the correct and recommended dose. Exceeding the recommended dose can cause liver damage. It’s important not to give fever-lowering medication too often or for prolonged periods, because it can cause side-effects.
Cool baths, sponging and fans can actually make your child more uncomfortable.
You must not give your child aspirin for any reason.
Aspirin can make your child susceptible to Reye’s syndrome
, a rare but potentially fatal illness. It can also cause serious illness or even death in children with chickenpox or flu symptoms.
Taking your child’s temperature
You might want to take your child’s temperature if your child is:
- unwell and feels warmer than usual
- irritable and crying
- more sleepy than usual
- in pain
- refusing to drink, or vomiting.
Using a thermometer is the best way to check your child’s temperature. Feeling your child’s skin temperature (for example, by putting your hand to her forehead) isn’t always a reliable way of diagnosing a fever. Your local doctor, maternal and child health nurse nurse can show you how to take temperature with a thermometer.
There are several different methods for taking a child’s temperature using a thermometer:
- orally (putting a digital thermometer in the mouth under the tongue)
- rectally (putting the thermometer a little way into your baby’s rectum)
- axillary (under the armpit)
- aurally (with a digital ear thermometer – shown to be a little inaccurate)
- superficially (with a temporal artery thermometer – this is a device you wipe across your child’s forehead to get a reading).
It’s hard to take an oral temperature if your child is under five because he might not cooperate. If your child has a blocked nose because of a cold, he might find it hard to breathe with his mouth closed.
To take an oral temperature, wait five minutes after your child has had a hot or cold drink (or it will affect the temperature), then place the thermometer well under one side of his tongue. Have your child hold it in place with his lips, not his teeth, and tell him to breathe through his nose. Wait until the thermometer ‘beeps’ before taking a reading. Oral readings can be around half a degree lower than body temperature.
Rectal thermometers are best used for babies and young children under 12 months (older children will probably protest loudly!). Rectal readings are most reliable for babies under three months.
Taking a rectal temperature is often difficult, especially when your baby is very active – the thermometer can slide out of the rectum, or the tip of the thermometer might damage the lining of the rectum. Place the tip of a digital thermometer just inside your child’s anus and wait for it to ‘beep’ before taking a reading.
Taking your child’s temperature under her armpit is usually the safest method, especially in young children. Unfortunately, it’s also the least accurate method.
Place the thermometer in your child’s armpit and close his arm, holding the elbow against the body. Wait for the thermometer to ‘beep’ before taking a reading. Armpit readings can record a temperature up to 1 degree lower than the actual body temperature.
Mercury thermometers can poison a child if they break. If you’re using a mercury thermometer, consider replacing it with one of the thermometers below.
Ear thermometers (infrared tympanic thermometers)
These are quick and easy to use. Your doctor or nurse can show you how to place the thermometer in your child’s ear canal, so you get a reasonably accurate reading. A plastic cover is placed over the tip of the thermometer, which is held gently just inside your child’s ear canal, until the thermometer ‘beeps’. It’s accurate to within about a degree, as long as the ear canal doesn’t have too much wax in it.
Temporal artery thermometers
These are relatively new, and are the simplest to use. The thermometer is scanned across your child’s forehead. It has the advantage of allowing you to check your sleeping child without waking him.
These are good if your child already uses a pacifier. Infants or toddlers who don’t use pacifiers will usually resist a pacifier thermometer, so something else might be easier to use.
Several other types of thermometers have been introduced in recent years, and are being marketed aggressively to parents. One method involves a plastic strip that’s placed on your child's forehead and gives a digital reading of the temperature. This system isn’t very accurate – at best, it can provide only a rough guide to your child’s temperature.