What Are Fever Dreams? The Science Behind Fever Dreams

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Temperature affects the way your brain works, and fever can produce waking hallucinations and vivid imagery as well as nightmares.

Some people find that too much spicy food leads to nightmares, and this may also be because it raises body temperature. Our temperature varies throughout the day and is especially low just before the onset of sleep. Then, during REM (rapid-eye-movement) sleep when most dreams occur, temperature control is very poor.

So having a fever can lead to a much higher temperature than normal during REM sleep, and it is this that causes the over-activity manifested in our minds as vivid and scary dreams.

What Is a Fever Dream?

The normal temperature of a human body usually ranges between 97 and 99 degrees. But when our body is fighting a virus, bacteria, or an infection our immune system goes into action. The core body temperature shoots up between two to seven degrees, triggering our body’s natural defense mechanism.

All kinds of bacteria, viruses, and infections are temperature-sensitive pathogens —higher temperatures prevent pathogens from multiplying in our bodies. Though having a fever is an uncomfortable experience, it is actually our body’s way of attacking harmful pathogens.

With a fever, we see symptoms like high body temperature, aches, chills, sweating, and sometimes bizarre dreams. The content of dreams like these, often disturbing in nature, leave a lasting impression accompanied by intense feelings.

There’s not a lot of scientific research behind fever dreams as of yet. However, there have been a few interesting findings, including a study done in 2013 published in the Journal of Pain and Symptom Management. One participant noted their fever dreams included a recurring dream they’d experienced during adolescence, returning with the fever. Another reported their fever dreams suddenly shifted in tone from positive to negative. According to the study authors, “The basic idea is that the ‘over-heated brain is not functioning properly and, therefore, dreams are more bizarre.”

A 2016 study compared reported dreams people had with a fever to regular dreams. 94% said the fever dreams were more negative than normal dreams.

Another more recent study, published in 2021, confirmed this idea, learning once again that fever dreams had a much more negative tone than regular dreams. This confirms what is known as the “continuity hypothesis” of dreaming. This states that dreams are a reflection of experiences from everyday life, including negative ones, and combined with the cognitive impairment caused by a fever, this can create a rather unpleasant night of sleep.

Some people woke up from their recent dreams feeling intense weakness, confusion, irritability, and helplessness, while others experienced acute heat perception, feeling extremely hot upon waking.

What Do We See in Fever Dreams?

Fever dreams are nightmares we experience as a result of having a high body temperature. These are emotionally intense and ghastly dreams with disturbing negative connotations. Since high body temperature makes it difficult to sleep, the disturbing nature of fever dreams increases sleep disruptions. Some of the common themes and visuals in fever dreams have been described as:

  • Associated with heat and fire, with visuals like the sky on fire or wax statues melting down. This could be because the body temperature is high and the brain triggers this heat, to keep pathogens at bay. The brain’s awareness of this high body temperature could be a probable reason behind fever dreams being associated with heat.
  • Repetitive actions or events.
  • Experiencing a fever dream can sometimes be like watching a sci-fi film, replete with images typical of the genre like spatial distortions, blackness, giant insects, and creatures with oversized arms moving around.
  • Strange dreams with a high recall value of every minute detail.
  • Often associated with something that is intimidating, and stress-inducing, sometimes from your own life experiences or external stimuli.
  • Sometimes fever dreams end with a feeling of claustrophobia or vertigo.


Does heat cause weird dreams?

Yes. The brain regulates our body’s temperature, and when we have a fever our body’s temperature increases to fight pathogens. Due to excess heat from the high body temperature our brain is unable to perform normally during a fever, it produces unpleasant and unusual dreams. There’s no foolproof way to kick your fever dreams to the curb, but controlling your body temperature at night can help. Take a warm bath before to force your body to cool down, and sleep with cool bedding, like cotton, bamboo, or Tencel.

Do you dream more when you are sick?

If you are down with a fever, sleeping becomes difficult due to high temperature and body aches. Disturbed sleep leads to emotionally intense dreams with a negative tinge to them. You may not remember your fever dream, but you could experience negative moods when you wake up. Try to eat easily digestible foods so as not to disrupt sleep any further, and try to sleep as much as possible to stave off the fatigue.

Can infections cause nightmares?

Yes, when your body is experiencing a fever or sickness, like the flu, you are more likely to experience nightmares because your brain is not functioning properly. If you have a fever, be sure to take fever-reducing medication like ibuprofen (acetaminophen) or aspirin, drink plenty of fluids, and get lots of rest.

Why are dreams so weird when sick?

Elevated brain temperatures could disrupt the brain’s normal cognitive processes, Schredl and his coauthors write in the paper. “The idea is that the brain is not functioning well during high fever,” he says, and this somehow produces dreams with unusual and unpleasant qualities

This article is for informational purposes and should not replace advice from your doctor or other medical professional.