What Is a Fever Dream?

When the body fights a virus like COVID-19 (or any other type of infection), its core temperature shoots up from its normal range (usually between 97 and 99 degrees Fahrenheit) to defend itself against temperature-sensitive pathogens like bacteria and viruses.

You have a fever if your temperature of at least 100.4 degrees Fahrenheit, per the Centers for Disease Control and Prevention (CDC). The higher the temperature, the harder it is for pathogens to multiply in our bodies.

Sometimes, people report having more intense or unusual dreams when they have a fever or say they're having "fever dreams."

What Are Fever Dreams?

The telltale symptoms of a fever are pretty recognizable: aches, chills, sweating—but in some cases, those dealing with a higher-than-normal body temperature may also experience vivid, sometimes disturbing, negatively-toned dreams known as "fever dreams."

Some people who have fevers due to COVID-19 have reported experiencing fever dreams. "I've heard reports of this happening in some people I know with the coronavirus infection," Alcibiades Rodriguez, MD, medical director of the Comprehensive Epilepsy Center-Sleep Center at NYU Langone Health, told Health. But these fever dreams aren't just COVID-19 specific—they can happen whenever a person's body temperature rises above normal.

Essentially, fever dreams are strange, often negatively-toned dreams one can experience with a higher-than-normal body temperature. Unfortunately, a lot of science behind fever dreams is lacking, but there have been a few studies on the topic. In one 2013 study published in the Journal of Pain and Symptom Management, 11% of people sick with a fever experienced fever dreams. One person in the study described a recurring dream they had during adolescence, which returned during a recent fever. Another reported dreams that switched from positive situations to negative ones.

Another study, published in 2016 in the International Journal of Dream Research, compared dreams people had during a fever to dreams they had when they weren't sick. Around 94% of those who experienced fever dreams described them as negative and more "emotionally intense" than regular dreams. Some of them talked about giant insects, "creatures with oversized arms and legs," and blackness "slowly spreading all over."

An online study published in January 2020 in the journal Frontiers in Psychology found that, out of 164 people, 100 had experienced recent fever dreams. According to the study authors, those fever dreams were "more bizarre and more negatively toned" than regular dreams. Many of the fever dreams also involved heat perception—one study participant described a dream in which they woke up from sleep because their body felt as if it was "blazing" and said, "the most intense feelings were weakness and helplessness."

What Causes Fever Dreams?

It's still unknown exactly why these strange dreams can accompany fevers, but experts have a few theories. "We don't exactly know why fever makes dreams more vivid and disturbing, although one theory is that the brain doesn't process sensations normally when we have a fever," Beth Malow, MD, a professor in the department of neurology and pediatrics and director of the sleep disorders division at Vanderbilt University Medical Center, told Health.

Dr. Malow said fever dreams are believed to be more frequent during the rapid eye movement (REM) stage of sleep. Most dreams occur during REM sleep, but temperature is also connected. "We don't regulate our body temperature during REM sleep as well as we do during other stages of sleep, and temperature can swing out of control," Dr. Malow said. Dr. Rodriguez added, "if we get a spike in fever during REM sleep, we may feel more uncomfortable and have micro-arousals (shifts between deep and light sleep). This increases the likelihood of us remembering our dreams."

Underlying Conditions

Of course, there's also a possibility that fever dreams might not always be dreams—or at least not as we know them. "We know in other medical conditions, such as encephalopathies [diseases that affect the function or structure of the brain], people may have hallucinations," said Dr. Rodriguez. "It is possible that hallucinations may be a form of 'awake dreaming' in those circumstances. The same could be said for when we have a fever."

Poor Sleep

The fragmented sleep that someone gets while sick may also contribute to strange dreams. "Having a fever is an unstable state that will fragment our sleep," said Dr. Rodriguez. "We know that patients with severe sleep apnea or narcolepsy, which both have a form of sleep fragmentation, have a tendency to remember more of their dreams." Dr. Rodriguez also pointed out that whether we have a fever or not, we usually remember the more disturbing dreams, such as nightmares.

Stress

Even if you're not ill with a fever, you may still be experiencing strange dreams—especially with added stress. From a psychiatric perspective, dreams are important in understanding unconscious thoughts, Gail Saltz, MD, an associate professor of psychiatry at the NY Presbyterian Hospital Weill-Cornell School of medicine and host of "Personology" podcast, told Health. "If interpreted correctly by a patient and doctor working together, a dream can provide a window into unconscious anxieties, fears, desires, etc.," Dr. Saltz said.

Potential Treatments for Fever Dreams

While you may not know precisely why a fever may cause vivid or disturbing dreams, and though there's not a surefire way to avoid them, the more steps you take to control your core body temperature, the more likely you are to get a peaceful night's sleep. That means getting plenty of rest, drinking lots of fluids (preferably water), taking the meds recommended by your healthcare providers, such as ibuprofen or aspirin, taking lukewarm baths or sponging exposed skin with tepid water, and trying to eat nutritious, easily-digestible foods.

Also important: If you're ill with COVID-19 and your fever results from that, make sure you self-isolate, manage your symptoms, and keep an eye on how you feel. If your condition worsens—like, if you start to experience shortness of breath or your fever spikes to over 103 degrees Fahrenheit—seek medical attention ASAP.

The information in this story is accurate as of press time. However, as the situation surrounding COVID-19 continues to evolve, it's possible that some data have changed since publication. While Health is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations for their own communities by using the CDC, WHO, and their local public health department as resources.