When the new coronavirus started traveling around the world, people were screened for fever to see if they might be ill with COVID-19.

That makes sense because fever is one of the first signs that your body is fighting an infection. But if fever is one of the body’s natural defenses, is it wise to take medicine to lower your fever…or better to let your fever do its job?

What does a fever really mean?

Most people assume that fever means an infection is assaulting your body, but fever actually is a signal that your body is fighting infection. Although individual baseline temperatures can vary slightly, fever is generally defined as a body temperature above 100.4°F. * Your body expends a lot of energy with a fever. For roughly every two degrees Fahrenheit of elevated body temperature, your energy expenditure goes up by 12%.

Here’s what happens: When a microorganism, such as a virus or bacterium, invades and attacks cells within your body, your immune system ­releases proteins (cytokines) that travel to your brain and reset your body’s thermostat to raise your temperature. The increased temperature, in turn, ramps up production of antibodies and white blood cells that travel through your body to attack the invaders.

What many people don’t realize is that lowering a fever with acetaminophen (Tylenol) or a nonsteroidal anti-­inflammatory drug (NSAID), such as ibuprofen (Motrin) or aspirin, can do more harm than good. Dozens of studies in animals and humans show that when you interrupt your body’s natural response by taking one of these drugs, your infection can cause symptoms that are more severe and last longer. 

If you feel tired and uncomfortable while running a temperature, that means your body is using energy to produce a fever. These symptoms, including chills and body aches, are your body’s way of telling you to stay in bed and conserve energy. Important: Fever is often due to a bacterial infection that may require treatment, such as an antibiotic, so consult your doctor.

When a fever is dangerous

For many people, fever can be frightening because they fear that a very high body temperature can damage the brain. This risk is real, but it depends on the cause of your fever.

A physiologic fever, which is caused by an infection, almost never causes brain damage. In fact, studies show that humans can tolerate very high temperatures, even as high as 106°F or 107°F, without damage.

Even febrile seizures, convulsions that can occur in children under age five when their fever spikes to 102.2°F or higher, do not cause brain damage or long-term problems, such as epilepsy or developmental delays.

An environmental fever is another story. This type of fever occurs when people are wearing heavy clothing or trapped inside a car during a hot, humid day, unable to dissipate heat through sweating. Environmental fever can cause heat stroke.

Older adults are at greater risk for heat stroke than younger adults because their bodies are less sensitive to temperature changes and they are more likely to become dehydrated. Taking certain medications, including laxatives, antihistamines and tricyclic antidepressants, also increases risk.

What to do if you have a fever

While most fevers are due to common cold and flulike viruses, fever also can be caused by cancer and diseases that cause inflammation, such as rheumatoid arthritis and lupus, or by a reaction to drugs, such as certain antibiotics. Let your doctor know about a fever that worsens, lasts for more than three days or keeps coming back.

Even though there are downsides to treating a fever, if your body temperature exceeds 103°F or is accompanied by other symptoms such as confusion, stiff neck, rash, severe pain or trouble breathing, call your doctor right away. While a physiologic fever doesn’t cause permanent harm, the symptoms in this case may be a clue to a ­severe illness. Otherwise…

  • Drink plenty of fluids.
  • Eat easy-to-digest foods, such as soups. Your body needs energy to heal.
  • Get plenty of rest.
  • Take a lukewarm bath.
  • Apply cool washcloths.
  • Stay home to protect others from any infection your body is fighting.

Note: Fever can increase heart rate and breathing rate, so consult your doctor if you have concerns. Fever of 100.4°F or above in a young baby may be due to an illness that requires treatment—talk to a pediatrician.

Related Articles