Doctors debate benefits and detriments of fevers

  • Fever is a sign the body is rallying to fend off an infection or illness.

    Fever is a sign the body is rallying to fend off an infection or illness. Stock Photo

  • Fever is a sign the body is rallying to fend off an infection or illness.

    Fever is a sign the body is rallying to fend off an infection or illness. Stock Photo

By Dr. Eve Glazier and Dr. Elizabeth Ko
Posted4/10/2021 7:00 AM

Q: I'm confused about fever. What is considered a fever? And if fever is the result of a person's body fighting a disease, why is it bad for us? It seems to make no sense to treat a person by lowering their fever.

A: You've asked a fascinating question that, believe it or not, has been a subject of debate for thousands of years.


As you point out, a fever isn't a disease. Rather, it's most often a sign that the body is rallying to fend off an infection or illness. What people haven't been able to agree on is whether or not the fever is beneficial because it fights the invader, or detrimental because of its damaging toll on our bodies.

One line of thinking goes that if an elevated core temperature is helpful at fighting off an illness, we shouldn't interfere. That's an idea that dates all the way back to Hippocrates. In fact, the practice of pyrotherapy -- medically inducing a fever -- was used as recently as the late 19th and early 20th century to manage certain types of bacterial infections. Pyrotherapy was largely abandoned once the discovery of penicillin ushered in the era of antibiotics.

The opposing argument is that the metabolic costs of having a fever outweigh the potential benefits. For example, even a moderate fever may pose a danger to people with heart or lung conditions, because it causes heart and respiratory rates to increase. Fever can also adversely affect the mental state of someone with dementia. That means in order to avoid potential complications, fever should be treated.

Small studies have yielded evidence that supports each side of the fever argument. The fact is that centuries later, we still don't have a definitive answer.

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What we do know is that fever is defined as a body temperature of 100.4 degrees Fahrenheit (that's 38 degrees Celsius) and up. The most common causes of fever are upper and lower respiratory tract infections, gastrointestinal infections and urinary tract infections. Heatstroke, sunstroke, certain cancers, reactions to drugs, allergic reactions and autoimmune disorders can also cause fever.

Symptoms that accompany a fever typically include headache, muscle aches, sweating, chills and shivering, loss of appetite, weakness and generally feeling crummy. Most adults can tolerate temporary fevers up to 104 degrees. However, this type of fever may signal additional underlying problems. We recommend checking with your doctor if your fever reaches 103 degrees or more.

To reduce a fever, adults and children over the age of 6 months can use over-the-counter medicines such as ibuprofen or acetaminophen. Although adults can treat a fever with aspirin, it should never be given to children; the use of aspirin in children has been linked to Reyes syndrome, which is a rare but serious condition that causes swelling in the liver and brain.

Taking a lukewarm -- not cool or cold -- shower, bath or sponge bath can also bring relief. You should rest when you have a fever, and drink plenty of fluids to stay hydrated. When any type of fever is persistent or becomes recurrent, it's important to see your doctor.


Q: A friend from work needs surgery for lung cancer. He was doing breathing exercises, which he said was part of prehab -- something I've never heard of. I don't want to bother him with questions, but am curious: What's prehab, and why would it be important?

A: Prehab is shorthand for prehabilitation, similar to rehab and rehabilitation. It's based on the idea that patients, by building up strength and stamina before their surgery, may be able to improve their post-surgical recovery.

Prehab first became common with orthopedic surgeries such as hip, knee or shoulder replacement; rotator cuff surgery, joint fusion and ACL surgery. These are procedures that require sustained physical therapy for the patient to recover full function. The thinking was that the enhanced fitness achieved through a program of prehab could help prepare orthopedic surgical patients for rehab, and thus ease and even speed their recovery process.

The concept of prehab gradually began to be adapted to other types of surgeries and procedures, including cancer surgeries.

Some people with non-small cell lung cancer diagnosed at an early stage may be helped by surgery. It's a complex procedure that can range from cutting out a small portion of the lung to the removal of the entire lung. Unfortunately, not all patients are suitable candidates.

Among the criteria that make a patient eligible is an assessment of the individual's physical condition, and whether they are physically fit for surgery; this includes having certain levels of heart and lung function. In some cases, these levels can be improved with a program of physical exercise, breathing exercises and other types of therapy. Some lung cancer patients deemed unfit for surgery have, with a targeted program of prehab, been able to improve their heart and lung function enough to go ahead with their procedure.

Prehab has also been shown to improve a lung cancer patient's recovery following surgery. In a study published in 2019, researchers followed two groups of patients undergoing surgery for non-small cell lung cancer. One group took part in a two-week prehab program. This included performing daily aerobic exercise, resistance training and breathing exercises, as well as following specific nutritional guidelines. They also received counseling and psychological support. The other group of patients had no special preparation prior to surgery. The study participants were evaluated one month after each of their surgeries. The group of patients who had participated in prehab was found to have better heart and lung function than the group that had no prehab.

So far, studies that quantify the benefits of prehab are limited. However hospitals that offer this type of approach say their patients feel supported by the programs. They report that the techniques they learn help them not only through the immediate aftermath of surgery, but into their long-term recovery.

• Dr. Eve Glazier is an internist and associate professor of medicine at UCLA Health. Dr. Elizabeth Ko is an internist and assistant professor of medicine at UCLA Health. Send your questions to

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