Rest Easy: You Don't Swallow Spiders While Sleeping

At some time or another, you’ve probably heard that humans swallow eight spiders a year while sleeping. No matter how you feel about spiders, you’ll probably be relieved to learn this isn’t true.

No matter what you've heard, we don't really swallow eight spiders a year in our sleep. (Photo via Shutterstock)

How this legend became a widely held belief is a mystery, but it's not rooted in any truth. In fact, the idea of humans swallowing spiders goes against both human biology and spider science. There’s also no scientific record or medical evidence to suggest we really do swallow spiders in our sleep.


Swallowing even one spider while sleeping in your lifetime would be noteworthy, so eight a year is pretty far-fetched. Why? For one thing, we usually sleep with our mouths closed. And if our mouths are open, we are likely snoring. The sound of us snoring would be enough to make spiders stay away.


In general, our sleeping bodies are not an inviting environment for spiders. We move in our sleep, and sometimes we snore and make other noises. And we're always breathing and our hearts are always beating. All these activities create vibrations, and these vibrations are like warning signals for spiders.


Spiders experience the world through vibrations, and the vibrations we create tell the spider to stay away. Also, even if spiders regularly crawled over our bodies in our sleep, all but the deepest of sleepers would probably be awoken by the feeling of a spider crawling across their face.


It's not just spider-loving scientists who are crying foul at this far-fetched myth. The National Sleep Foundation says it is very unlikely that swallowing a spider in your sleep happens even once in your lifetime, let alone repeatedly.


While it may be possible to swallow a spider in your sleep, it's unlikely enough that it would be considered a random event, not something that happens regularly or frequently. So don't lose sleep over this silly myth, or the fact that there are almost certainly spiders in your house. It's normal, and no cause for concern.


Most homes in North America have three or four species of spiders living inside, but they mean the human inhabitants no harm. Spiders are usually either tending to their webs or trying to stay out of our way. And they will kill most insects in our homes, providing a natural form of pest control.


Some of the common indoor spiders we see in Illinois are cellar spiders, cobweb spiders, sac spiders and brown spiders. The majority of indoor spiders are harmless to humans. One, the brown recluse spider, can be dangerous, and it is sometimes found in houses. However, these spiders try to avoid people, and they aren't aggressive. They rarely bite, and most brown recluse bites do not cause serious injury.

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