EachNight may earn commissions for products you purchase through links on our site. Our articles include affiliate links and advertisements, including Amerisleep, LLC advertising. Learn more Updated February 3, 2021While we dream every night, when we’re sick, our dreams can be particularly vivid or frightening. The intense dreams we experience during an episode of high body temperature are called fever dreams. Sometimes these dreams are just abnormally dramatic and memorable, but for some people, they can be really upsetting.So what exactly is a fever dream? When do we get them? Why do we have them? Below, we’ll answer these questions and give you some info on what to do if you’re experiencing disturbing dreams every time you catch the sniffles.When We Get Fever DreamsOf course, the most obvious time we get fever dreams is when we have a fever—a core body temperature over 100.4 degrees Fahrenheit. Our normal body temperature is between 97 and 99 degrees. When we’re fighting infection, one of our immune system’s main defense mechanisms is turning up the heat. Most viruses and bacteria thrive when our body is at its normal temperature, so upping the temperature by a few degrees makes it a lot harder for temperature-sensitive pathogens to survive. This means you’re most likely to have fever dreams when you have an infection or some other illness that causes your body to experience higher temperatures than normal.However, there are other scenarios where you can still experience fever dreams. For instance, if your core temperature is raised because of conditions outside of your body (like heavy wearing layers when it’s warm outside or spending too much time in the sun)—an issue called hyperthermia—you can experience hallucinations and fever dreams. In fact, these can be symptoms of both heat exhaustion and heatstroke.Why We Get Fever DreamsSince nobody knows for sure why we experience regular dreams in the first place, the same holds true for why we experience fever dreams. Scientists believe high core body temperatures disrupt the brain’s ability to think normally, leading to lower cognitive function and sometimes even wake time hallucinations.Combine the feverish brain’s cognitive impairment with the fact the core body temperature rises during Rapid Eye Movement sleep (REM sleep), and this increased elevation may impact your brain’s normal dreaming activity, leading to intense or unpleasant dreams.What Fever Dreams Are LikeAll fever dreams are vivid, but the bad news is the overwhelming majority of people who experienced them identified them as upsetting. When you’re having a fever dream, you may experience more intense emotions, more bizarre narratives, and/or more harrowing situations than during your normal dreams. These strange dreams can and do interrupt sleep. They also have some common themes.Heat or FireA lot of times the content of dreams induced by fever might include things like forest fires, melting objects, or heat waves. This might be due to the brain’s awareness of the body’s elevated temperature.Stressful or Intimidating SituationsSome people reported dreams like recurrent childhood nightmares suddenly returning to them in adulthood. Many also reported feeling endangered during recent fever dreams. You might experience anxieties about death, accidents, violence, or personal phobias during one of these bizarre dreams. Negative dream emotions like sadness and fear and scary health-related themes are also common.Fantastical ElementsFever dreams often involve bizarreness such as alien creatures, distorted sensory perception, and vastly different environments from real life.Higher Dream Recall ValueAnother big thing about fever dreams is they have a high dream recall frequency, meaning you remember them more often than regular dreams. This could be due to their intensity or unpleasantness, and it could also be because these dreams tend to interrupt REM sleep with more frequency. When your sleep is disturbed during a dream, you’re more likely to remember that dream.How to Prevent Fever DreamsFor some people, intense dreams while they’re sick don’t really bother them, but for others, fever dreams are often nightmares that can cause anxiety surrounding sleep, fear of falling asleep, or in the severest of cases, psychological trauma. There’s no magic bullet for all fever dreams, but if you want to prevent them, controlling your core body temperature is a good start.To keep your fever down:Eat foods that are easy on the stomach (like those on the BRAT diet)Drink lots of fluidsGet plenty of restTake an NSAID like ibuprofen or aspirin to lower feverShower in lukewarm or cool waterFAQsIs a fever dream the same as a lucid dream?Not really. While these dreams are both extremely vivid, lucid dreams happen when you know you’re asleep and dreaming. This consciousness can sometimes allow you to learn to control the content and narrative of your dreams. By contrast, fever dreams are entirely out of your control and you normally aren’t aware they’re dreams while they’re happening.Is it bad to sleep with a fever?No. A fever isn’t like a concussion. In fact, if you’re sick, sleep is an important part of getting better. Rest can help boost your immune system and get you well again faster, and it also allows your body to devote more energy to healing itself rather than other things like working, studying, or exercise.Why are fever dreams so often nightmares?There’s not really a clear answer to this one. We know the body has a harder time controlling its internal temperature during the REM stage of sleep. We know fever raises the core temperature. And we know body temperature has a profound effect on cognition. But why all this seems to lead almost exclusively to bizarre and unpleasant dreams, rather than fun and enjoyable dreams, is still mostly a mystery that might never be solved by future studies.Do other species experience fever dreams?While we know other animals besides humans experience dreams (dogs are a good example), there’s not much research on whether they have more intense dreams during illness. However, since animals do have complex and vivid dreams, and they’re also similar to humans in a number of other ways, it wouldn’t be implausible to think they can experience fever dreams while they’re sick.Are fever dreams ever a sign of something serious?Since fever dreams can occur for nothing more than a common cold, they’re not a sign of serious illness in and of themselves. However, if you have a persistent fever or illness, there could be something else going on. The general rule is if you have mild symptoms like a low-grade fever or stuffy nose that last more than a week or two, you should see your doctor.Also, if you have a high fever—over 103—it’s a good idea to call your doctor right away. Remember, any fever over 104 is an emergency because it can cause lasting brain damage.Bottom LineFever dreams are always vivid and often upsetting, but thankfully they’re not normally dangerous on their own, and they tend to go away when your illness does.If you have disturbing fever dreams frequently, the best way to prevent them might just be to avoid getting sick. Wash your hands frequently, don’t drink or eat after others, and avoid touching your face as much as possible. Your brain and your body will both thank you.About the author Kiera PritchardKiera Pritchard’s curiosity around dreams and dreaming sparked her passion for sleep science. In addition to freelancing for eachnight, Kiera is also a physical trainer and strives to help others lead healthy lives while asleep and awake. Since joining our team, Kiera has compiled multiple sleep health guides offering our readers advice on how to improve their days and evenings. 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