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FalseScienceLast updated: June 1, 2026

You swallow spiders in your sleep

The claim that people swallow an average of four to eight spiders per year while sleeping is an urban legend with no scientific basis. Both spider and human biology make this scenario extremely implausible, and no documented cases exist in scientific or medical literature.

What we know

This myth circulates in various forms, with the figure of eight spiders per year or 20 per lifetime being common. Arachnologists, biologists, and medical professionals consistently describe it as having no factual foundation.

From the spider's perspective, a sleeping human represents a poor environment. The vibrations from breathing, snoring, and heartbeat would register as threatening stimuli to a spider, which avoids large vibration sources as they indicate potential predators. The warm, humid environment of a human's open mouth, combined with exhaled breath, would also be actively repellent. Spiders have no reason to explore the mouth of a large breathing animal.

From the human side, people who sleep with their mouths open typically snore, creating vibrations and airflow that would deter any approaching spider. Even in unusually still, open-mouthed sleepers, the conditions described above would need to be overcome simultaneously for a spider to accidentally enter. Dr. Geoff Oxford of the British Arachnological Society and Dr. Matt Wilkinson of Cambridge University's zoology department both characterize the claim as a myth. The Burke Museum of Natural History confirms that no such case is on formal record anywhere in scientific or medical literature.

The origin of the specific figure of eight spiders per year has been attributed to a 1993 article by columnist Lisa Holst, who reportedly compiled a list of implausible statistics people accept as true, though the original article is difficult to verify.

Common claims

  • People swallow 8 spiders per year while sleepingNo scientific evidence or documented cases
  • Spiders are drawn to human mouths while people sleepFalse - human vibrations and breath deter spiders
  • Swallowing sleeping spiders is harmlessIrrelevant - event does not reliably occur

Evidence hierarchy

01Scientific American - Fact or Fiction: People swallow 8 spiders per yearExpert analysis explaining why spider and human biology make this scenario essentially impossible and noting the lack of eyewitness evidence.02Burke Museum - Myth: You swallow spiders in your sleepBurke Museum arachnology collection confirms no documented case exists in scientific or medical literature.03BBC News - Do people really swallow spiders in their sleep?Expert commentary from Cambridge University zoologist and British Arachnological Society confirming the myth has no basis.

All sources

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