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Hot Garbage: Mythbusting fever in children


Juniper is a 3yr old girl brought in with her mother, with a 48hr history of fever. Her mum is particularly concerned because her fever was up to 39.8°C, didn’t come down with paracetamol and she describes an episode which sounds like a rigor. On examination, she has a temperature of 39.3°C, a runny nose and bright red tonsils, and looks otherwise well. You go to discharge her, but your colleague asks if you should wait to see if her temperature comes down with ibuprofen before sending her home.


Febrile illnesses are the most common cause of presentation to acute paediatric medical services. This means that fever is the most common presenting symptom seen by paediatricians, and it is a massive cause of concern for parents. Despite this fact, it is clear that in day-to-day practice, there is a widespread misunderstanding about fever, its purpose, and its clinical interpretation.

Well, no longer! Once you have finished reading, you will be a master of all things related to fevers in children. We will start with a basic understanding of the processes surrounding fever and finish with some mega myth-busting!

What is fever?

Fever is an elevated core body temperature, part of a physiological response to infection regulated by the hypothalamus. This is crucial to understand – your body controls your temperature. This is not something an infection is doing to your body; it is something your body is doing to the infection. This differs from pathological hyperthermia, where your temperature is elevated by either hypothalamic dysfunction or external heat. These are extremely rare.

Note: there are other non-infectious causes of fever, such as cancer, Kawasakis, and autoinflammatory conditions, but these are rare compared to infectious fever and are covered elsewhere.

What temperature counts as a fever?

At what threshold do we say a child has an elevated body temperature? This is more controversial than one might think, as the data from which we derive “normal” body temperature is extremely poor. The most common cut-off for defining a fever is 38°C – but it is important to remember that there is nothing magic about 38°C compared to 37.9°C, and temperature is better taken in context or a trend, if possible.

How do we get fevers?

The process of developing fever is extremely complex, and our understanding is still developing. At present, our best explanation is that the process is triggered by the presence of chemicals referred to as pyrogens. Pyrogens can either be exogenous (such as parts of the microbe itself, like the lipopolysaccharide on the outside of bacteria), or endogenous, such as cytokines like IL1, TNF, Prostaglandin E2 and importantly IL6, which are released by immune cells when they detect an invader. These pyrogens act to increase body temperature peripherally, but importantly also trigger receptors in the preoptic nucleus in the brain. This releases PGE2 into the hypothalamus, which then sets a new target temperature. This target is met by many facets designed to increase heat, including:

  • Release of noradrenaline by the sympathetic nervous system, increasing thermogenesis in brown adipose tissue and causing peripheral vasoconstriction and piloerection (reducing heat loss)
  • Acetylcholine release stimulating muscle myocytes to induce shivering
  • Feeling cold”, inducing heat-seeking behaviours (warm clothes and blankets)

It is important to remember that the body is trying to get hotter. If you intervene with non-medicinal efforts to cool it down, it will work even harder to try to heat up.

Why do we get fevers?

The process of having a fever has been conserved across species from lizards to mammals, and even plants! This is because it is a beneficial response to an infection. The mechanisms by which a fever helps protect you from infection include:

  1. Higher temperatures inhibiting growth/replication of pathogens
  2. Higher temperatures promoting the immune response to infection

It is also worth noting that bacteria are killed more easily by antibiotics at higher temperatures, so there is also a potential third mechanism.


Fever is beneficial. When a pathogen causes infection, pyrogens stimulate the hypothalamus to increase the body temperature through several mechanisms. This increased temperature helps inhibit the growth of the pathogen AND stimulates the immune system to fight it.

That was a lot of science. Don’t worry – it’s time to get clinical! All this science stuff is lovely, but what does this mean for our patients?

Clinical significance of fever

As we have ascertained, fever is beneficial. For this reason, it is of no concern when a child presents with fever alone. What we are interested in is the reason for the fever. Is this fever the result of a benign, self-limiting childhood infection – or is it associated with a severe bacterial infection? Trying to determine whether this is enough for its blog article (the most important thing is the end-of-the-bed assessment – see Andy Tagg’s excellent breakdown of the paediatric assessment triangle).

Ignore the fever itself – what’s important is ascertaining its cause.

Now, let’s get on and bust some myths that persist surrounding fever in children!

Myth 1 – Higher temperature indicates a serious infection

This is one of the most common concerns among parents. The particular height of temperature may be what prompts them to come to hospital or even what drives the health care provider to initiate more aggressive management or investigations.

The truth is that the relationship between the height of temperature and risk of serious illness is at best complicated, and at worst a dangerous distraction. There is a very poor correlation, with such woeful sensitivity and specificity that it will both grossly over and under-call serious infections (either if the high temperature is used to rule in, or lower temperature to rule out). The caveat to this is in younger infants (particularly under 60 or 90 days), who have a higher baseline risk of serious infections (and more to the point – once they spike a temperature will be managed aggressively regardless of how high it was). Some studies have shown a fragile association in older children, but not enough for it to have any meaningful influence on our management. A fever is a fever – higher temperatures should not be managed differently than lower ones.

Myth 2 – Temperature not relieved by antipyretics indicates a serious infection

Another common misconception is also linked to the myth above. Some fevers respond well to antipyretics, and some do not. We do not understand why this is the case. However, studies have not demonstrated that failure to respond to antipyretics is a helpful indicator of a more serious infection. It is not very pleasant for the child to remain hot, but it does not mean they are at any higher risk. A child whose temperature does not respond to antipyretics should not be treated any differently than one that does.

Myth 3 – Rigors indicated a serious infection

This has been covered in a separate blog post – but to summarise, there is extremely weak evidence that rigors are associated with an increased risk of bacterial infection in children, which is irrelevant when more important factors are taken into account. There is also evidence of no increased risk. The presence or absence of rigors should not be a deciding factor in managing febrile children.

Myth 4 – You must wait for a fever to come down before discharge

This may seem common practice for many of you working in acute paediatrics. If a child is febrile on arrival, people often want to wait to see the temperature come down before allowing them to be discharged (this should be differentiated from seeing observations normalize in the absence of fever – which is a more understandable, if still slightly questionable practice). As we have seen, a fever merely indicates the presence of an infection. If you have ascertained the cause of the fever or at least ruled out any red flags for serious causes, the ongoing presence or absence of a fever means nothing for the child. If it comes down before discharge, it will probably just go up again once they are home! There is no need to make them wait for hours for no reason.

Myth 5 – Fever should be treated with antipyretics

We have established that fever is beneficial. Therefore, there is essentially no reason to treat a fever in and of itself. It will not cause harm, and it is probably helping. Some children tolerate having higher temperatures exceptionally well, so if they are playing happily or do not seem terribly bothered about their temperature of 39°C, then you leave them well alone.

Treat the child, not the fever.

Myth 6 – Fever should not be treated with antipyretics

There is an opposing school of thought, which says that since fevers are beneficial, we should not treat them at all. Given how absolutely dreadful it can feel to have a fever (which many of us adults should be able to vouch for), many of us give medicines to try to bring the temperature down and make the child more comfortable. This is the right thing to do. Despite the potential benefits of having a fever, there is no evidence of any clinically significant harms to treating temperatures in unwell children or adults in ICU. If the child is distressed by the temperature, they should have antipyretics to make them feel more comfortable.


  • Fever helps your body to fight infection and is not dangerous (no matter how high)
  • The fever itself is not important. The cause of the fever is what matters
  • There is little to no evidence that higher temperatures, temperatures that don’t respond to antipyretics, or rigors indicate an increased risk of serious infection
  • Persisting fever on its own is not a reason to postpone discharge
  • Only treat fevers if they are causing distress. Treat the child, not the fever

Postscript: Febrile convulsions

When I posted my initial thread on twitter about fevers, there were many comments asking why I didn’t address febrile convulsions. This was mainly because these are worth a post to themselves (which they have here). In brief, febrile convulsions are extremely distressing for parents to observe, but they are common and they are very benign. We do not advise treating fevers to prevent febrile convulsions, and until recently, this was because there was no evidence that they had any effect in preventing them. A recent study from Japan did demonstrate a decrease in the recurrence of febrile convulsions in children who had already had one if given regular PR paracetamol; however, there are significant caveats to this study discussed in depth here.

For the more visual oriented, the talented Emma Buxton has created an infographic of the key reminders from this blog post:


  • Alasdair Munro is a Paediatric registrar in the UK, currently working as a Clinical Research Fellow in Paediatric Infectious Diseases. His interests include evidence based medicine, diagnostics and antimicrobial resistance. @apsmunro | Ally's DFTB posts


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8 thoughts on “Hot Garbage: Mythbusting fever in children”

  1. Mohammed ِAlhussain

    Great topic
    Thanks Dr. Munro
    It would be great if you have included the following 2 myths as well:
    1: Rectal acetaminophen is better than the oral form!
    2: Alternating acetaminophen and ibuprofen is better than sticking to acetaminophen or ibuprofen (if needed) alone!

  2. Convulsions, irrespective of being febrile origin or not can be scary particularly to parents because of its potential indication of a neurological disorder. Thus the need for the availability of timelier and more effective therapeutics. Additionally, indicators for differentiating between convulsions of febrile origin from other causes as well as raising public awareness of these indicators can reduce unnecessary clinical work-up and over expectation of medical interventions from parents.

  3. I wish more GPs and health visitors would read this: so many health visitors tell parents to give calpol at the slightest hint of fever, and that they Must see Gp. GPs often perpetuate the idea that anti-pyretics should be given regularly to keep the fever down, and don’t explain to parents that actually fever is a good (albeit sometimes unpleasant) symptom, which reduces the rate at which viruses replicate, therefore hopefully shortening the illness. I tend to advise giving anti-pyretics only if miserable /in pain (especially if preventing them from taking fluids). I think fever is often a distraction to parents, and that we should be teaching parents about more important symptoms and signs (e.g. anuria).
    Great article.
    DOI: GP, gp trainer, medical student educator, urgent care GP.

  4. Thanks for your feedback Cath, it’s important in social media communities that different viewpoints are reflected, so thank you for taking the trouble to comment. I understand your concern that an unexplained tachycardia is a dangerous entity and in serious review, after serious review, it crops up as a missed opportunity. It is vital though when applying principles to practice the best evidence base is used. There have been numerous studies now demonstrating “in isolation” derangement of individual variables does not increase mortality or morbidity (Bubbles wraps 10 and 12). This is why scoring systems, situational awareness and good communication are the suggested outcomes from national reports, case reviews and coroners courts rather than specific instructions that a single variable should be used to determine decision making. Alasdair was quite clear in this post about using fever ‘alone’ as a decision making mechanism and also highlighted that resolution of other variables is a part of normal practice (with the caveats that the evidence based is mixed on this). A further common cause of error is overcrowding in emergency departments and assessment units. Clearly the reasons for this are multifactorial but one reason is the number of myths that perpetuate about how long children have to wait prior to discharge. This seems incongruous but if we were able to spot the well child more effectively and send them home then the needles would be easier to spot as the haystack becomes smaller. I do not dispute that sepsis is a critically important condition but our obsession with numbers rather than the child in front of us is missing a more important approach of actively listening to parents, observing behavioural change and providing safety net advice based on trajectory of illness. We’ll take on board perhaps we could have added in positive approaches to take with managing fever rather than just the negatives. Thanks again for taking the time to engage.

  5. I think this post is a little naive and overly reassuring for Paediatric trainees.
    Fever can be a very important sign of sepsis and if used as an excuse for tachycardia can lead to children with untreated sepsis being discharged. Whilst factually correct it is overly reassuring and indicates lack of experience with critically ill children who appear well but are sitting on the edge of the physiological cliff. Rather than highlighting the risks for the child this post falsely reassures discharge without discussing when it would be dangerous to do so. We all see fevers at home and in the course of our work all the time and it is important for educators of trainees to highlight when fever is forming part of a more serious picture for a child. Doctors should maintain a healthy wariness of sepsis and importantly listen to the carer/mother’s concerns and importantly observe the tachycardia come down with deffervescence prior to discharge.