Fever Facts You Need To Know

*The Well is proud to present the following content in partnership with Northwell Health-GoHealth Urgent Care centers. This piece originally appeared on GoHealth’s Health Library and has been republished on The Well with permission.

The human body is designed to function best within a narrow temperature range, typically within a degree or two of the “normal” average of 98.6 degrees F. While many people use the term “fever” loosely, meaning they feel flushed or warmer than usual, the medical criteria for a fever is 100.4 F or higher. When your body runs hotter than that, it’s a sign that your immune system is in attack mode because it’s perceived a threat. Bottom line: When you’re sick, in most instances, fever is your friend.

Here are five more things you should know about running a fever:

The hypothalamus, commonly referred to as the body’s “thermostat,” is located in the brain. A person develops a fever when the hypothalamus shifts the body’s set point to a higher temperature. When this happens, you can feel flushed or feverish—paradoxically, you also can experience chills because your 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.

Infections are the most common reason why a person would run a fever. When the body is invaded by a pathogen, the hypothalamus raises the body’s internal temperature to a level the pathogen can no longer survive in. The higher temperature kills the pathogen and helps resolve the infection.

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

Patients with prolonged or recurrent fevers should seek medical attention to rule out a non-infectious condition that can be dangerous if left untreated.

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

A person can quickly become dehydrated from a fever, even if they’re not losing fluid from vomiting or diarrhea. Why? Because water evaporates faster off hot surfaces. So the hotter your skin temperature, the faster fluid will escape from your body.

Small children become dehydrated faster than older children or adults, but anyone suffering from fever should be encouraged to drink plenty of clear fluids. Fever-reducing medication is useful with high or prolonged fevers because it will help to lower the skin temperature and slow the rate of fluid loss.

For children between the ages of 6 months and 5 years, it’s important to look out for febrile seizures. These fever-induced seizures occur when the body’s internal temperature rises rapidly. While febrile seizures usually last only a few minutes and do not indicate any dangerous underlying condition, any child with a fever who has a seizure should be taken to a doctor immediately to rule out a more serious diagnosis like meningitis.

The treatment for a fever depends on several things, including the source of the fever, duration, severity of symptoms, age of the person with the fever, and any underlying medical conditions.

Most fevers that are a result of a viral infection resolve on their own within 96 hours, and don’t require any specific treatment (though rest, oral hydration, and over-the-counter medications that alleviate pain and reduce fevers are recommended).

For bacterial infections, antibiotics may be necessary. Fungal infections can be treated with antifungal medications. But the treatment for fevers caused by non-infectious sources depends on the specific diagnosis. So, when in doubt, be safe and call your health care provider.

• Learn more about Northwell Health-GoHealth Urgent Care centers.
• What’s the best way to treat my child’s fever?
• Is it cold, flu, allergies, or COVID-19?
• What's it really like to have the flu?