Do Spiders Bite You in Your Sleep? Mostly Not
Spiders very rarely bite people in their sleep: they do not feed on blood, and a spider that ends up on a bed usually leaves without biting. Rod Crawford of the Burke Museum estimates a spider might wander onto a bed as often as twice a year, and fewer if bedding does not touch the floor or walls. Most marks found in the morning are bites from blood feeders such as bed bugs, fleas and mosquitoes, or are not bites at all: in one emergency department study, 85.7% of patients who arrived with a “spider bite” were diagnosed with a skin infection.
The belief that “if you did not see what bit you, it was a spider” is old. Crawford notes it was already well established in a medical article from 1901, and it still sends people to doctors and pest professionals for the wrong problem. This guide sets out what actually bites at night, what the medical studies found when they checked supposed spider bites, and where the swallowed-spiders statistic came from.
What bites at night, if it is not a spider?
| Culprit | Feeds on blood? | When and where it bites | Clues |
|---|---|---|---|
| Bed bugs | Yes | At night while people sleep (CDC); face, neck, arms, hands | Marks may appear one to several days later, up to 14 days in some people; adults 1 to 7 mm |
| Fleas | Yes | Any time; mostly ankles and lower legs (Penn State) | Small red spot with a red halo (UC IPM); usually a pet in the home |
| Mosquitoes | Yes (females) | Day and night (CDC); house mosquitoes most active dusk to dawn | Itching and swelling soon after; one in the room at night is often the answer |
| Kissing bugs | Yes | Mostly at night while people are asleep; sometimes on the face (Texas DSHS, Texas A&M) | Found in 29 states, most in Texas, New Mexico and Arizona; adults about 1/2 to 1 in long; bites often painless |
| Bird and rodent mites | Yes | Indoors after nesting birds or rodents leave | Near a nest, vent or attic |
| Spiders | No | Only defensively, when trapped against skin | Usually a single mark; a spider found and kept is the only real evidence |
Richard Vetter, an entomologist at the University of California, Riverside, put the medical advice plainly in the Western Journal of Medicine: if arthropods are involved at all, physicians should think first of creatures that seek mammals for blood meals, such as ticks, fleas, bed bugs and assassin bugs, rather than accidental spider bites. Our bite identification guide covers how far the mark itself can narrow it down, and why one partner can be bitten while the other shows nothing.
Do spiders bite in your sleep?
Almost never. The Burke Museum’s explanation has three parts, and each is worth knowing.
- They have no reason to. Spiders are not bloodsuckers and, in Crawford’s words, are not aware of our existence in any case. A sleeping person is not prey.
- They rarely get there. Unless you sleep on a basement floor, a spider might reach a bed perhaps twice a year. Keeping blankets and bedspreads off the floor and walls makes it, in Crawford’s phrase, effectively zero.
- Rolling on one rarely causes a bite. Spider fangs are underneath the body. A spider pressed from above may reflexively bite what it is standing on, which is the sheet, not you.
True spider bites, Burke says, happen when a spider is trapped inside clothing, when someone reaches into spider habitat without looking, or when someone slaps at one crawling on them. A bed is a poor fit for any of those, which is why a shoe, a glove or a pair of trousers left on a garage floor is the more likely place for a real bite.
Do spiders bite humans for no reason?
No. A spider bite is a defensive act by an animal that is being squeezed. Spiders do not bite humans for blood, and they do not seek people out. If marks keep appearing night after night, that pattern itself points away from spiders, because a defensive bite does not recur on a schedule.
How common are spider bites while sleeping?
No study counts bites in bed specifically, but the studies that checked supposed spider bites against evidence leave little room for them. The best known is from the University of California, Irvine, where 182 emergency patients who said a spider had bitten them were followed to their diagnosis.
Seven of the 182, 3.8%, were diagnosed with an actual spider bite, and where the species could be identified it was a black widow. 156, or 85.7%, were diagnosed with infections. The author expected many to be community-acquired MRSA, and the Burke Museum lists MRSA among the leading causes of alleged spider bites.
A large Australian study adds the other half of the picture. Of 750 definite spider bites where the spider was caught and identified by an expert, significant effects occurred in 6%, no bite caused a necrotic ulcer, and secondary infection occurred in 0.9%. Real spider bites, in other words, are usually minor; the dramatic sores blamed on spiders are usually something else.
Is it common to get bit by a spider in your sleep?
No. Spider bites of any kind are uncommon, and the bedroom is one of the least likely places for one. Crawford’s summary of morning bumps is that they are generally caused by non-bite disease conditions, and the minority that really are bites come from blood feeders, less often mites or ticks. Genuine spider bites in this situation are possible, he says, but very rare.
The brown recluse problem: diagnoses without spiders
The clearest evidence that spider bites are over-diagnosed comes from the brown recluse, the US spider most often blamed for a sore that appears overnight. Its range is limited to the South and central Midwest, which makes the numbers easy to test.
- South Carolina. Physicians in the state diagnosed 478 brown recluse bites in 1990 and 738 in 2004, yet only 44 brown recluse specimens had been verified there since 1953, from six locations.
- California. Vetter found verification of fewer than 10 brown recluse specimens in more than 40 years of state records and no populations at all, while several hundred “brown recluse bites” were reported to him in a decade.
- A Kansas house. Over six months, 2,055 brown recluses were collected in an occupied 19th-century home in Lenexa, at least 400 of them large enough to bite, and no one living there was bitten.
That last finding matters most for this question: a household lived with a heavy recluse infestation for months without a single bite. Vetter’s list of conditions misdiagnosed as recluse bites includes staphylococcal and streptococcal infections, shingles and herpes, Lyme disease, diabetic ulcers, fungal infections, poison ivy and chemical burns. Some of those need prompt treatment, which is why a doctor should see any sore that is spreading, hot, or comes with fever. For telling a real recluse from its lookalikes, see our spider identification guide.
How do I know if a spider bit me in my sleep?
In most cases you cannot know from the mark. The only reliable evidence is the spider itself, caught at the time. The Burke Museum’s advice is to save the spider that bit someone for identification by a professional arachnologist.
| What you notice | What it more likely means |
|---|---|
| Two marks side by side | Usually a blood feeder that bit twice, or one eruption with two heads. In any spider smaller than a tarantula the fang marks are too close together to see as two (Burke Museum) |
| Rows or clusters of itchy bumps, new ones on later nights | Bed bugs are worth checking; see do bed bugs bite every night |
| Bites on ankles and shins, pets in the house | Fleas |
| A painful, spreading, red or pus-filled sore | Often a skin infection; see a doctor |
| A spider found crushed in the bed and a single painful mark | Possibly a spider; keep the spider for identification |
Searching for spider bite pictures rarely helps, for the same reason: the conditions in Vetter’s list can look alike, and a photograph of a mark cannot show which animal, if any, made it. For any bite with severe pain, muscle cramps, spreading redness, fever or a growing sore, see a doctor; for advice on a known spider bite, call Poison Control on 1-800-222-1222.
Do we swallow spiders in our sleep?
No. The Burke Museum states that no case of a sleeping person swallowing a spider is on formal record anywhere in scientific or medical literature, and asks why, among the millions of people who have watched someone sleep, there is not one eyewitness account of a spider trying to enter a sleeper’s mouth. The numbers in the various versions do not even agree: Burke has heard four a year, 20 in a lifetime, and a pound in a lifetime, which would be over 20,000 spiders.
The origin story is nearly as shaky. Snopes credits a 1993 PC Professional column by Lisa Holst, said to have invented the statistic to show how readily people believe lists of facts. A University of Sheffield historian, writing for the university’s History Matters blog in 2015, notes that people have tried to trace Holst and her article without success, so the claim that it was a deliberate test has by no means been confirmed. The myth of a planted myth may itself be a myth.
Small animals do occasionally turn up in ears, which is a separate and real question; our article on whether cockroaches can live in your ear covers it.
Do spiders crawl on you at night?
Rarely, and less than people fear. Most spiders seen indoors belong to a few house-adapted species that stay hidden in crawlspaces, wall voids and storage areas, and Burke notes that fewer than 5% of the spiders you see indoors have ever been outdoors. The ones that wander into the open are usually adult males searching for mates in late summer.
Our analysis of iNaturalist research-grade records shows that pattern. Adjusted for how much people are recording each month (100 is the yearly average), all spider records peak in September at 184. The common house spider peaks in September and October at 174 and 172, and the hobo spider, whose males wander in search of females, jumps from 33 in June to 286 in August. These are records of where and when people photographed spiders, mostly outdoors, not bite rates. Cellar spiders, which live indoors all year, stay much flatter.
The night biters follow different calendars. Mosquito records peak in September at 182 and fall to around half the average or less from December to April. Bed bug records do the reverse, peaking in December at 174, but bed bugs live indoors year round, so that winter rise most likely reflects people noticing and recording them when little else is about, not more biting. The practical point is that a run of winter bites in bed is very unlikely to be mosquitoes or wandering spiders.
How to keep spiders off the bed
- Keep bedding off the floor and walls. This is the step Burke says brings the chance of a spider on the bed to effectively zero.
- Do not store clothing on the floor, and shake out shoes, gloves and clothes left in garages or basements, since trapped spiders cause most genuine bites.
- Vacuum webs and egg sacs from corners and under furniture. Our guide to getting rid of spiders in the house covers what works and what does not.
- Check for the real night biters. Look along mattress seams for bed bugs and check pets for fleas before blaming spiders. Bed bugs are a job for a licensed professional in most homes.
- Do not spray the bedroom for spiders because of unexplained marks. If you use any product elsewhere, follow the label.
Frequently asked questions
How do I know if a spider bit me in my sleep?
Usually you cannot tell from the mark. Spider fangs are so close together in all but the largest spiders that a bite rarely shows two separate punctures, and many skin infections and insect bites look alike. The only reliable evidence is the spider itself, caught and kept for identification. Repeated new marks on later nights point to bed bugs or fleas, and a spreading painful sore needs a doctor.
How common are spider bites while sleeping?
Very uncommon. The Burke Museum estimates a spider reaches a bed perhaps twice a year, and usually no bite results because spiders are not blood feeders and their fangs face downward. In a University of California, Irvine study, only 3.8% of 182 emergency patients reporting a spider bite were diagnosed with one, while 85.7% had infections.
What is biting me in my sleep?
Most often a blood feeder. Bed bugs bite at night while people sleep and their marks can take up to 14 days to appear; fleas bite mainly the ankles and lower legs; mosquitoes bite day and night; kissing bugs, most common in Texas, New Mexico and Arizona, feed mostly at night. A mark with no insect found may also not be a bite at all, so a doctor should see anything that spreads or blisters.
Is it common to get bit by a spider in your sleep?
No. Genuine spider bites happen mainly when a spider is trapped in clothing or a hand goes into its hiding place unseen. In a Kansas home with 2,055 brown recluses collected over six months, nobody was bitten. Keeping sheets and blankets from touching the floor or walls makes a spider on the bed very unlikely in the first place.
Do we swallow spiders in our sleep?
No. The Burke Museum states that no case of a sleeping person swallowing a spider is on record anywhere in scientific or medical literature. A spider has no reason to approach a large, breathing, vibrating person. The popular figure of eight spiders a year has no source; even the story that a columnist invented it in 1993 has never been confirmed.
Sources
- Burke Museum of Natural History and Culture, Spider Myths (Rod Crawford): Spiders bite sleeping persons; You swallow spiders in your sleep; Spider bites leave two punctures; Spiders come indoors in the fall; Spiders cause infection with fangs.
- Suchard JR. “Spider bite” lesions are usually diagnosed as skin and soft-tissue infections. J Emerg Med, 2011.
- Isbister GK, Gray MR. A prospective study of 750 definite spider bites, with expert spider identification. QJM, 2002.
- Vetter RS. Myth: idiopathic wounds are often due to brown recluse or other spider bites throughout the United States. West J Med, 2000.
- Vetter RS, Barger DK. An infestation of 2,055 brown recluse spiders and no envenomations in a Kansas home. J Med Entomol, 2002.
- Frithsen IL, Vetter RS, Stocks IC. Reports of envenomation by brown recluse spiders exceed verified specimens of Loxosceles spiders in South Carolina. J Am Board Fam Med, 2007.
- Vetter RS, Bush SP. Reports of presumptive brown recluse spider bites reinforce improbable diagnosis in regions of North America where the spider is not endemic. Clin Infect Dis, 2002.
- Centers for Disease Control and Prevention, About Bed Bugs; About Mosquitoes; Life Cycle of Culex Mosquitoes; About Fleas.
- University of California Statewide IPM Program, Pest Notes 7419: Fleas.
- Penn State Extension, Cat Fleas.
- Texas A&M University, Kissing Bugs and Chagas Disease in the US; Texas Department of State Health Services, Kissing Bug and Chagas Disease Guide.
- Snopes, Do People Swallow Eight Spiders Per Year?
- Parker R. Hard to swallow? Myths and cultural memes about spiders. History Matters, University of Sheffield, 2015.
- The Pest Control Brief analysis of iNaturalist research-grade records, pulled October 2026.
