The claim:
Humans sometimes swallow spiders (as many as eight per year) while we’re sleeping.
The science:
The thought of an eight-legged critter crawling across your pillow, climbing your face and creeping into your mouth while you sleep is the stuff of nightmares. As you ponder that image, consider this: For even one spider to end up in your mouth would require a series of unlikely events. Here’s why:
- Spiders want nothing to do with humans. The notion that a spider would come anywhere near a sleeping, snoring human is antithetical to spider behavior. There are thousands of species of spiders, but only a handful live in human homes. The vast majority of spiders that live indoors are small and relatively harmless, spinning webs. Some, such as wolf spiders, actively hunt insects, including mosquitoes, flies and even small cockroaches.
- Your open, moist mouth isn’t appealing to a spider. Spiders breathe oxygen and would be repelled by your mouth, which to them would seem like “a warm, moist cave that is mostly carbon dioxide and water vapor,” said Floyd Shockley, an entomologist and the collections manager at the Smithsonian National Museum of Natural History. Vibrations from any snoring also would scare them away, he said.
- The odds are against it. Although it’s theoretically possible a spider could accidentally end up in your mouth, it’s highly unlikely. A spider would have to lose its grip while crawling across your bedroom ceiling at the precise moment it is positioned over your face and then fall squarely into your open mouth. “You’ve got a better chance of winning the Powerball than having a spider fall in your mouth while you’re sleeping,” Shockley said.
What else you should know:
This myth has taken various forms. Both a Guardian article and a Snapple cap “Real Fact” repeated the notion that the average human swallows eight spiders in a lifetime during sleep. (A Snapple spokesperson said that the “fact” was “retired” in 2014.)
In 2001, Snopes repeated a variation of the claim, asking the question “Do people swallow eight spiders a year in their sleep?” It told the story of Lisa Birgit Holst, who in 1993 included the claim in an article for “PC Professional.” Snopes has since acknowledged that both “PC Professional” and the columnist were fake, and this origin story was a joke. The name Lisa Birgit Holst is an anagram for “This is a big troll.”
The bottom line:
The odds of a spider falling or crawling into your mouth even one time are virtually zero.
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If it ever did happen, take comfort in knowing that a swallowed spider would land in stomach acid and die almost instantly, “with no harm done to the human,” said Bill Shear, professor emeritus of biology at Hampden-Sydney College in Virginia and former president of the American Arachnological Society. “In fact, a little extra protein would have been obtained.”
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