Five Fast Facts About Fevers

The human body is designed to function best within a certain temperature range. The average “normal” body temperature is 98.6 degrees F.

While many people use the term “fever” loosely, meaning they feel flushed or warmer than usual, the medical criteria for fever is a temperature of 100.4 F or higher.

On average, children get fevers more frequently than adults do, and their fevers tend to run higher than adults’.

As the U.S. enters its cold and flu season this year, in addition to grappling with increasing rates of COVID-19, it’s important for patients to understand the ins and outs of fevers. Here’s what you need to know:

1. Fevers are regulated by your brain.

The hypothalamus commonly referred to as the body’s “thermostat,” is located in the brain. A fever happens when the hypothalamus shifts the body’s set point to a higher temperature. When this happens, patients can feel flushed or feverish. Paradoxically, patients also can experience chills because their current body temperature is lower than the new set point. Also, chills and shivering cause rapid muscle contractions that help raise the body’s internal temperature.

2. The most common cause of fevers is infection.

Infections are the most common reason why patients run fevers. Most microorganisms have a narrow temperature window in which they can survive. Sometimes this window is as narrow as 2 degrees F.

When the body is infected with a pathogen, the hypothalamus raises the body’s internal temperature to a level at which the pathogen can no longer survive, which defeats the pathogen and resolves the infection.

3. Other conditions can cause fevers as well.

While infections are the most common source of fevers, other non-infectious conditions can cause fevers as well. Certain cancers, autoimmune disorders, medications, and heat-related illnesses can cause fevers.

Patients with prolonged or recurrent fevers should seek medical attention to rule out these non-infectious fever sources since these conditions are often dangerous if left undetected or untreated.

4. Fevers can cause complications.

While a fever usually indicates a healthy immune system’s appropriate response to the presence of an infection, fevers can cause complications in certain situations.

Patients can quickly become dehydrated from a fever, even if they’re not losing fluid from vomiting or diarrhea because water evaporates faster off hot surfaces. So, the hotter your skin temperature is, the faster fluid will escape from your body. Febrile patients can also lose fluid from excess sweating.

Small children become dehydrated faster than larger children or adults, so it’s especially important to be vigilant of their hydration status. Febrile patients should be encouraged to drink plenty of clear fluids. Fever-reducing medication is often useful in patients with high or prolonged fevers to lower the skin temperature and slow the rate of fluid loss.

Another complication that children between the ages of 6 months - 5 years can experience is a seizure due to the fever. These are called febrile seizures.

Febrile seizures are triggered when the body’s internal temperature rises rapidly. While febrile seizures usually only last a few minutes and do not indicate any dangerous underlying condition, any child with a fever and a seizure require immediate medical attention to rule out a more serious diagnosis, including meningitis.

5. Several treatments for fevers are available.

The treatment for a fever depends on several factors, including the source of the fever, duration, and severity of symptoms, age of the patient, and any underlying conditions.

Most fevers due to viral infections resolve on their own within 96 hours and don’t require any specific treatment -- though patients may benefit from rest, oral hydration, and over-the-counter medications that alleviate pain and reduce fevers.

Bacterial infections are often treated with antibiotics, and fungal infections can be treated with antifungal medications. The treatment for fevers caused by non-infectious sources depends on the specific diagnosis.


Written by Sarah Thebarge, Physician Assistant