What is a fever:

A fever is anything over 100.4 degrees Fahrenheit or 38 degrees Celsius. Anything less than that is not considered a fever in the medical field.


How to take a body temperature:


This is the most accurate temperature because it is closest to the core body temperature. Always use a digital thermometer! The temperature is taken by inserting the silver tip into the rectum.  This is the recommended way to take temperatures in children under the age of 3 or 4, as long as they aren’t fighting you!! 


This isn’t as invasive as taking a rectal temperature and is recommended in children over the age of 4. You should usually add around 1 degree to the temperature reading because breathing out of the mouth may lower the temperature reading. It really doesn’t matter if the thermometer is under or over the tongue. The most important thing is making sure you don’t take it soon after they have either drank or eaten anything, as it could give a falsely elevated or low temperature reading.


Temperatures performed this way are done by placing the thermometer under an armpit.  This method, however, is not a very accurate way to take body temperatures so I would recommend against using it. 


These are thermometers that take body temperatures by either rubbing the thermometer on the skin or inserting it in the ear. I would not recommend thermometers that rub on the skin as skin temperatures vary greatly.  Infrared intra-ear thermometers are a good choice. However, if you don’t trust the readings, get a rectal temperature.


How the body produces fever:

Whenever there is an infection, there are signals that the body produces that alarm the area of the brain called the hypothalamus. The hypothalamus raises the “thermostat” in order to make the body inhospitable to the virus or bacteria that have invaded the body.  Your liver ramps up your metabolism which burns energy for heat. Your muscles may also to contract rapidly which causes chills or rigors. Those chills are the body’s way of raising your body temperature. Also, because the goal is to retain heat, sweat is not produced.


Is fever dangerous:

The short answer is no. Fever is the body’s natural way of fighting infection. Before antibiotics (Penicillin) in the 1940s, that was all humans had. If fever was bad, we would have died as a species thousands of years ago.  One of the dangers, however, is dehydration. Dehydration is characterized by dry mouth, rapid heart rate, significantly decreased urination or wet diapers, and weakness. Fever causes more water loss than usual and so if your child is not keeping themselves hydrated, they could get very ill. Although often a concern, fever by itself won’t cause brain damage. If brain damage occurs, it would be from the illness itself and not from the fever. 


When to be concerned about fever:

Fever by itself isn’t an emergency. However, fever that is associated with difficulty breathing, severe headache, stiff neck, severe vomiting, bloody diarrhea, bruising, confusion, dehydration, or lethargy (excessive sleepiness), is always an emergency.  Please note that a higher temperature does not mean the illness is more serious. You can have a viral illness with a 104.5 fever and a ruptured ear infection with a normal body temperature. I would also be concerned about fever in a child who has a weakened immune system due to chemotherapy, an immue deficiency, or high dose steroids.


Neonatal Fever:

Any fever in a child less than 2 months of age is always an emergency and they need medical attention.  These are unvaccinated babies who are at risk for serious bacterial infections such as meningitis and pneumonia, and these should be ruled out by either their pediatrician or an ER physician. 


Do you have to treat fever?

Nope.  Fever is a good thing as long your child is drinking well and isn’t seriously ill. Fever reducers, Tylenol and Motrin have only been around for 60+ and 50+ years respectively.  Some of your parents and/or grandparents were born in the time that fever simply had to run its course….and they survived!!!! Yes, childhood mortality was higher then, but they didn’t have vaccines and antibiotics that could prevent or treat diseases such as bacterial meningitis, polio, or Diphtheria. Fever has been showed to strengthen immune systems during an illness. Sometimes it is good to just let their body’s do what God designed it to do, especially if they aren’t significantly ill.


When to treat fever:

I would recommend that you treat their fever if they are uncomfortable, fussy, whiny, or if they ask for it.  The good thing is that acetaminophen and ibuprofen are also pain relievers.


How to treat fever:

Acetaminophen and Ibuprofen are the only 2 fever reducers recommended in children.  Aspirin is also considered a fever reducer but shouldn’t be used in children. Dosages for Acetaminophen and Ibuprofen are usually based on how much your child weighs. I would recommend talking to your child’s pediatrician for appropriate dosage and frequency instructions. Acetaminophen can be given at all ages, but Ibuprofen should only be given to kids over the age of 6 months. Placing a child in a cold bath, although it may sound like a good thing, could actually make them worse by causing intense rigors or chills. I wouldn’t recommend it to bring down fever.


Febrile seizures:

Febrile seizures often are a common concern when I talk to parents about fever. The vast majority of febrile seizures occur right as the fever has started and is often the first sign something is even wrong. Because of this, you are unlikely to prevent febrile seizures with fever reducers before they happen.  Although the literature sometimes states otherwise, I would always make sure your child is seen if they have a febrile seizure to ensure there isn’t a major illness such as meningitis.


I hope this blog gives some clarity about fever. It’s not something that should be feared, especially if your child is doing well.  As always, if you are concerned, don’t ever hesitate to seek medical attention.

Keith Perkins Jr., MD Dr. Perkins is a double board certified physician in Internal Medicine and Pediatrics and is the solo owner of Premier Internal Medicine and Pediatrics in Selmer, TN. He has been a practicing physician since 2011 and absolutely loves primary care.

You Might Also Enjoy...


This blog gives a quick overview of bronchiolitis often called "RSV".


This is a brief overview of measles.