I think fevers are so misunderstood. There is a surprising amount of misinformation surrounding them, a general misunderstanding of what actually constitutes a fever, and lots of confusion surrounding their physiology and treatment.
They are also extremely common, among children especially but also adults. As I am planning an upcoming post on preparing for vaccine appointments (and then likely a series of appointments afterwards about the different appointments in the first year of life), I thought it might be wise to first cover this topic since fevers are often a concern for parents after vaccinations (but more on this later).
What do we know about fevers? Actually the results of my poll were pretty mixed. People knew a good amount on the topic, and I was happy to see many of the common myths I’ve heard repeated were not believed to be true by most of the respondents. There was a lot of mixed responses around febrile seizures though, which I will cover in this post.
*Disclaimer: This blog is intended for informational purposes only. The information on this blog should not be used as a substitute to medical advice or medical treatment. As always, your Primary Care Provider, a doctor, or another health professional is your best resource for specific questions and medical advice. If you believe you or a loved one are experiencing a medical emergency, please contact 911. Note: As an Amazon Associate I earn from qualifying purchases.
So, what is a fever?
A fever is a physiological response, involving the hypothalamus (which is involved in many of your automatic responses – aka, the ones you don’t have to think about like your heart beating), that can occur for a variety of reasons.
Human beings are usually in and around 37-38 degrees Celsius (or 98.6 to 100.4 degrees Fahrenheit) body temperature but this varies depending on time of day (and person – dependent on age as well). Temperature may also vary throughout the day as a result of physical activity and environment.
Without getting too scientific, when someone has a fever, something triggers the hypothalamus to increase the temperature goal and therefore, increase heat generation and decrease heat loss in the body to meet this goal.
Shivering and other symptoms of fever are often a result of the body trying to increase heat production to meet the new temperature.
A fever generally is said to be a temperature of >38°C (varies dependent on source, as well as how you measure it). However, it’s not to be mistaken with hyperthermia – the primary difference being the cause (hyperthermia, in simple terms, occurs when the hypothalamus fails to regulate body temperature).
84.9% of 159 voters on my polls knew this – great job!
What can cause a fever?
It’s important to remember that a fever is what I described above, and not just the sensation of feeling hot – this could accompany a fever, but you’d have to take your (or your loved ones) temperature to know for sure.
It is also important to know that a fever itself is not an illness, but a sign of an illness.
The most common causes of a fever are infection (various – bacterial or viral), tumors and cancers (various), and inflammation. Some drugs may also cause a fever.
In children, the most common cause of a fever is infection.
Other possible causes include fever as a result of immunization/vaccination and to 62.6% of voters disbelief – overdressing. This usually only produces what is called a “low-grade” fever (this is defined differently dependent on source as well, however it generally it is considered a higher temperature that is just below 38°C/100.4°F). Due to the cause being environmental though, I question whether this is actually a form of hyperthermia (several sources listed it as a “cause” of a fever). So, if you said this was incorrect you may not be wrong – but it is a common cause of a raised temperature in a baby, so if you notice your baby is warm a good first step is to check if they are overdressed.
If anything I write here ever needs correction, feel free to shoot me an e-mail at: email@example.com!
Is teething a cause of fever?
Studies show mixed results, but most seem to show that fever is often misreported by parents – one study from 2016 showed that just under 50% of parents reported fever in their teething child. However, it should be noted that a “fever” was considered at 37.5°C and above in this study – which is actually consistent if temperature is measured orally. The study also showed a relationship between occurrence of fever during teething with some factors such as ethnicity, tobacco exposure, and C-section birth, which is interesting.
A meta-analysis (a study looking at multiple studies done on the subject) from earlier the same year however, found that only ~25% of babies and children experienced fever associated with teething. It was found that fever was often misreported in this 25% though (aka the temperature was under what is usually considered a fever).
So, it seems a big issue to address in patient education for us healthcare providers is making sure parents/caregivers know what is actually is considered a fever. And parents/caregivers – don’t be afraid to ask questions, or give your nurse/physician’s office a call if you aren’t sure about your child’s temperature reading.
Speaking of temperature reading… what is the best way for me to measure my child’s temperature?
In my mind, what is best is what the parent is most comfortable with.
The most accurate way to measure the temperature of a child who is <5 years old is… via rectal measurement (91.6% of 107 voters got this correct).
After 5, the most accurate way to measure a child’s temperature is via oral measurement.
Rectal measurements can be daunting to think about though and many parents (reasonably so) do not feel comfortable doing them. That is okay – as I said, I think the best method is what you feel comfortable with.
The next best option is an axillary measurement (under the armpit).
If you are OK with doing a rectal measurement, I recommend asking for guidance from your HCP or nurse. There are online resources as well, however I still recommend going to your HCP first for guidance. Armpit works well – just keep in mind there are slight differences in temperature readings based on where you take them from.
To the 31.5% of voters who said ear was the next best – this also works, if your child is over 2 years old.
*Please make sure you are using a digital thermometer for readings. Here is the one I have (I highly recommend the brand Braun) – I used this pre-pregnancy for a bit when my water broke and I had to take my own temperature, as well as for Maggie afterwards. If your child is >2 years old and you are looking for an ear thermometer – Braun also makes one available on Amazon! (Please note, as an Amazon Associate I earn from qualifying purchases).
Do all fevers require treatment/medication?
70.2% of 104 voters said it depends on their symptoms, and this is the correct approach to take when assessing the need for medication with a fever.
For a child who is over 3 months old, a fever may not need treatment (antipyretic medication such as Tylenol for example) if they are otherwise acting normally – meaning they are eating, sleeping, and acting as they normally do.
However, if the fever occurs with other symptoms of illness, lasts >24 hrs, or goes over 40°C/104°F, you should contact your healthcare provider.
Additionally, all fevers in children under 3 months old warrant a call to the HCP (medication dosage would also be needed from the HCP for babies < 3 months old). There are several other reasons why you should contact your HCP immediately with fever, which can be found here under “When to see a doctor”.
If you are ever unsure what to do, or something doesn’t feel quite right with your baby/child – contact your HCP.
I think it’s important to note here that Ibuprofen should not be given to any children <6 months old, and Aspirin should not be given to children or teens at all. Once again – contact your HCP with any specific questions and for any guidance as needed.
But if I don’t treat my child’s fever, won’t it keep increasing? Then they will be at risk for brain damage or other complications such as febrile seizure.
54% of 100 voters said this was false.
So, an increased temperature can cause brain damage and death – however this is more often seen with hyperthermia than it is with fever and that has to do with the cause of each, which I mentioned earlier on.
With a fever, the hypothalamus is like a thermostat that has a new set temperature; with hyperthermia, the hypothalamus has lost control of the temperature entirely. This means that with hyperthermia, there is more of a chance of temperature increasing to a level that the body cannot handle – especially the brain.
Fevers, even without medical treatment, do not usually exceed maximum 105°F/40.6°C, though some sources say they don’t usually even exceed 103-104°F. It is also important to note that even with medication, your child’s temperature may still be at fever level and fluctuate for several days as their body continues to fight off the infection (when infection is the cause).
Even very mild or short episodes of hyperthermia can cause symptoms of decreased brain function and a handful of other problems or complications. If you’ve taken first aid, they talk pretty extensively about heat stroke and hyperthermia – which may seem silly until you realize how serious both of these can be for the body. Overdressing a baby – who is still “learning” how to regulate their internal thermostat and doesn’t do it very well at the beginning – is therefore something you should be mindful of!
What about febrile seizures?
47.5% of 99 voters believed that febrile seizures could cause neurological complications, and 44.9% of 98 voters believed that febrile seizures were common.
Febrile seizures are not as common as one might think – they affect only ~2-4% (source dependent) of children <5 years of age. Risk does increase if there is a family history of febrile seizures however (in the siblings and parents). Also, they are still the most common type of seizure in children.
Like most forms of seizure, they may be scary to witness if you have never seen it before (and because it is happening to your child!), however they are not known to cause brain damage or any other neurological/developmental issues.
The risks that do exist for febrile seizure?
They may be associated with an increased the risk of epilepsy, but having a one-time episode of febrile seizure does not mean your child has or will eventually develop epilepsy (most do not).
A child who has had a febrile seizure may also be at risk to have other episodes of them, especially if they are <18 months at first occurrence, have a family history (as I mentioned), or a few other criteria you can see here.
If your child has a febrile seizure at home, contact your HCP for further guidance + to make an appointment for assessment (this will always be my advice). You can also take normal seizure precautions such as making sure the environment is safe, not restraining your child or putting anything into their mouth to bite down on (this is a common belief of something to do during a seizure), and time the length of the seizure (5+ minutes = call 911!).
Will giving my child Tylenol (or other medication) after vaccines prevent febrile seizures?
Actually, no. If your child does not have a fever post-vaccination, then giving Tylenol just because will not prevent febrile seizures from happening. Remember also that not all fevers need to be treated!
Follow the advice of your healthcare provider – many will give you information about after care at your immunization appointment – what to do if your child does have a febrile seizure, when to give Tylenol/other medication for fever, and so on.
My child has a fever, so I will give them an ice bath.
A bath may be nice for your child – but it should not be icy cold.
Since bath water is changing your child’s environment, it may help to cool them down (physically but it likely will not affect your child’s internal temperature, or if it does it will only be a slight change), but lukewarm is an acceptable and comfortable temperature. Using very cold water may cause more temperature regulation issues. Not to mention – would you enjoy an ice bath? Most people would not.
Shivering in the bath, with or without fever, indicates that the water is not at the right temperature. The mechanism behind shivering can actually worsen a fever, so you want to avoid this by making sure the water is not too cold.
What other non-medical interventions are possible?
- Maintaining your child’s environment (the home + how much clothing they have on) at a comfortable temperature
- Increase fluid intake (age appropriate choice for which fluid is offered – ie. don’t offer a 3 month old water, but formula or breast milk)
- If they have a fever but still feel well, still make sure they don’t overdo it!
Feed a cold, starve a fever. I’ve heard that before, is it true? Should I have my child fast when they have a fever?
This adage is based on a very old recommendation, from Hippocrates! Yes, the same one from the Hippocratic oath… from ancient Greek times. In the 1800s, for a time the recommendation actually evolved to “feed” a fever, instead of starving it.
There is some science behind this – as starvation can increase the immune response but it seems to be only in response to bacterial infections and not viral (and most of your colds and fevers are caused by viral infections). It may actually decrease the body’s response to viruses, so I’d say it’s probably wise not to purposely change your eating habits because of this saying.
Ask your healthcare provider though if your child is having trouble eating or is not interested in food during fever or other illness – there are some recommendations that may be helpful.
If I need to give my child medication for fever, what is the best way to administer it?
Note: I had a question also about the difference in effectiveness between ibuprofen & acetaminophen for fever treatment specifically – according to one study from 2017, there is very little difference between the two (it may be child/body dependent would be my only thought and likely influenced by many factors?). There, according to the same study, may be some benefit to alternating between the two for fevers that are particularly stubborn (however, the American Academy of Pediatrics (AAP) in an older report do not recommend combo therapy – please let me know if this has changed; also please always follow what you are prescribed by your provider as they know your child & their case best).
I did find an older meta-analysis on this question though (from 2010) which seemed to show that ibuprofen (Motrin) is more effective for fever treatment. A self-report based study from this year also showed that patients reported ibuprofen to be more effective than acetaminophen for fever – keep in mind this is self-report from parents on a mobile app, however it is still interesting.
This report from the AAP does also show similar effectiveness for treatment of fever with both drugs, but that Ibuprofen may have longer lasting effects.
My take on this: preference based, unless there are any particular increased risks to either for your child (and your child is >6 months for the ibuprofen). Good discussion topic for your next HCP appointment or with your pharmacist – who is the expert on this!
If anyone has more recent recommendations/information on this – I’m looking at you pharm Twitter – then please feel free to share with me so I can update this (DM on Twitter or firstname.lastname@example.org!)
Now, back to med administration.
Administering a drug such as acetaminophen (Tylenol) in children for fever can be done two ways: oral (usually preferred, understandably – liquid form for young children or tablets) or rectal (suppository). They are both shown to be equally effective at reducing a fever. The rectal form is useful when a child is vomiting and cannot keep medication down however.
Similar to the way you take a temperature, you do what you are comfortable with & what your provider advises or has demonstrated for you to do safely. If you do need to administer a suppository to your child, Sick Kids has a great page with instructions on how best to do this (but again – check with your provider if you have any concerns, questions, or need guidance).
Before giving any medication, you may need to contact your provider/pharmacist regarding dosages and safe administration methods. Make sure you do any measurements of oral medication with the provided syringe (Tylenol provides one in the Infant Tylenol boxes) and not with household measurement items like spoons (not accurate). You can get syringes and other measurement tools at the pharmacy as well.
Make sure you give the dosage that is prescribed by your provider or that is the recommendation from the pharmacist or the one for the specific medication based on your child’s current weight (this is why you may need to contact your provider and why I would recommend it).
Get the advice of your provider on how to administer oral medications effectively. Some tips are:
- The syringe should go into the mouth but not into the back of the throat (choking risk) – a good tip is to try to administer towards the cheek (so between gums and cheek)
- Make sure you have your child in an upward position – it’s often easier to do this with two people if possible
- An older child can hold the syringe, this might help them feel more comfortable with the whole process
What if my child vomits the medication?
This is a common occurrence in children and babies. The answer is of course drug dependent, but generally with acetaminophen if the vomiting occurs within 20 minutes of the dose being given, you can safely administer a second dose of the same amount.
Before doing this with acetaminophen or any medication – check with your provider or pharmacist. If your child is vomiting a lot they may need further attention or a different form of medication (ie. suppository).
Remember to contact your healthcare provider (or pharmacist, nurse health line, etc.) with any specific questions regarding your child & fever. This blog is for informational purposes only and your provider should always be your first source of information regarding your child’s health (because they are the most knowledgeable on the topic + the most reliable resource you have!).
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