Don't fear the fever

This much misunderstood symptom is actually good for you, although it doesn't feel like it

Young children (especially those under 5 years) are the main frequenters of acute medical care, and febrile illnesses are the most common reason parents seek medical attention. Fever is much feared by both parents and many health professionals alike.

But it shouldn’t be.

It’s time to set the record straight! Understanding fever can help us take better care of our children and remove some of the stress from long nights with poorly little ones.

What is fever, and what causes it?

Fever is a raised body temperature, generally considered to be over 38°C or 100.4°F (this cut off is somewhat arbitrary and has an interesting history of its own). For children this will almost invariably be caused by an infection with a virus, or less commonly a bacteria (whilst there are other causes of fever, they are rare and we will not address them here).

A fever occurs when your body recognises a certain set of chemicals in the blood called pyrogens. These can either come directly from an invading bug or be released by immune cells when they discover one. Pyrogens stimulate a part of your brain called the hypothalamus, which is responsible for regulating your temperature. When the hypothalamus detects pyrogens, it sets a new, higher target temperature to achieve, and sets about sending signals to the rest of your body to help warm you up.

The body will try to heat up by standing hairs on end, re-directing blood away from the skin and peripheries into the core, by shivering, and by engaging in warming behaviours - feeling cold and trying to do things to warm up, like covering up with a blanket.

The fever is something the body is doing to the infection, not something the infection is doing to the body. Because the body is in control, it will not cause itself harm.

A fever in response to infection will not harm your child.

Why does fever happen?

Fever is a protective response to infection. It is a response conserved across many domains of life - even some plants get fevers when they have an infection! One of the most famous examples is of the desert iguana, which is cold blooded so needs to mechanically warm itself when it has an infection. If you prevent them from doing so, they die.

So how does a fever help? The bodies response to fever is complex, but our best understanding is that higher temperatures activate different parts of the immune system, as well as slowing down the growth of the invading virus or bacteria.

Should we treat fever?

Whilst fever may be of benefit to fighting infections, we also know it often makes children feel awful. This is actually part of the protective effect, as feeling unwell and going to bed all day stops you from infecting other people. However, we don’t like children to feel awful, so we will often treat them with medicines such as paracetamol or ibuprofen which are relatively effective at switching off the fever mechanism.

This is different to mechanical attempts to reduce the body temperature. Whilst the body is still under orders from the hypothalamus to get warmer, if you try to physically cool down the child then their body will only work harder to try and heat up. This is why we do not advise cold baths, flannels, stripping children down, or sitting them by open windows. Light clothing appropriate for the ambient temperature is fine.

Given that a fever is supposedly beneficial, should we avoid treating it at all? Fortunately, there appears to be little to no harm to treating fevers with medicine, so any theoretical risk is outweighed by the symptomatic benefits of treatment.

Some children can tolerate really high temperatures very well, and if they seem comfortable there is no need to treat them at all.

When your child has a fever, treat the child - not the temperature.

But what if it’s really high?

If the fever is in response to an infection (which is almost invariably the case) then the height of the temperature doesn’t matter. Your childs body will not make itself so hot that it would come to harm. In addition, the height of the temperature has no significant correlation to how likely the child is to have a more serious infection.

Similarly, it is not important whether the temperature subsides after giving medicines such as paracetamol or ibuprofen. Sometimes fever responds really quickly to these medicines. Sometimes it does not. Whether it responds or not is not an indicator of how worried you need to be about your child.

When should I worry?

When a child has a fever, this is just a sign that there is an infection. As children’s doctors, we are not concerned about the fever. We are concerned with what infection is the fever a response to. Is it a benign, childhood viral infection which will self resolve, or are there signs of a serious bacterial infection which needs treatment?

The overwhelming majority of infections in early childhood are caused by benign, childhood viruses which self resolve. Even mild bacterial infections, such as ear or throat infections, will resolve without treatment in most children.

The advice I often give parents is to try and remember the last time you had a nasty flu like illness, and how you felt.

That is likely how your child feels, and you should expect them to behave accordingly! Some good rules of thumb are:

• It’s OK for your child to want to sleep all day, but it should be easy to wake them up

• Its OK for your child to be clingy and unsettled, but they should be consolable with cuddles or the things they normally enjoy

• It’s OK if your child doesn’t want to eat for a while, so long as they are managing to drink reasonable amounts and pass urine 2 - 3 times a day (if they are very little and not eating, it is useful to get them to drink things with some sugar in them, such as milk or juice)

• It’s OK if your child develops a rash, so long as it goes pale when you apply pressure or stretch the skin, and it doesn’t look like bruising

For a really excellent resource on fever in children I highly recommend the healthier together website (it also has resources for many other common medical complaints in children).

Other reasons why you might need to seek medical attention if your child has a fever would include if they are less than 90 days of age (this time period is higher risk for serious bacterial infections), if they have had a fever for longer than 5 days (after which point a health professional should review to ensure there are no non-infectious causes of fever), or if they have medical conditions which predispose them to severe or complicated infections.

What about convulsions?

Young children have a lower seizure threshold than adults, and having a fever lowers your seizure threshold further. It is well recognised that as a result of a fever, some children can have seizures. We call this a febrile convulsion, or febrile seizure. These do not appear to be related to the height of the fever. Most evidence suggests that even by aggressively treating fever with medicines you cannot prevent a febrile convulsion - if it’s going to happen, it will happen, and you cannot prevent them.

The good news is, that febrile seizures are a very benign condition. If your child has had one, you will know that they look terrifying, and witnessing one can be quite traumatic for parents. However, they are not a serious risk to the childs wellbeing. The overwhelming majority of them are short, end without treatment, and have no lasting consequence. It is normal for children between the ages of 6 months and 6 years to have up to 6 episodes of febrile seizure. For more information about febrile convulsions you can read here.

Summary

• Fevers in young children are common, and most often due to viral infections which will resolve without treatment.

• The fever itself is of no harm to the child and is not concerning - it is the body helping to fight infection! More important is how the child seems in themselves, and whether they have any symptoms which are more than you would expect from a mild illness (imagine yourself with a flu like illness as a frame of reference).

• If the fever is making the child uncomfortable you can treat it with medicines, but do not physically cool them down.

• Febrile seizures can happen, but you cannot prevent them from happening and they are almost always benign when they do occur.