Do We Really Swallow Spiders While Sleeping?

Do we swallow spiders in our sleep?
Do we swallow spiders in our sleep?. Getty Images/Cultura/Kevin C. Moore

When I was a kid, I remember having earnest debates with my friends over how many spiders people swallow while sleeping. Arguments ranged from 4 spiders swallowed per year, to a full pound of spiders swallowed in a lifetime. What we all knew for certain was that we did swallow spiders in our sleep, probably almost every night.

Adults are no less gullible than kids, apparently, as shown by Lisa Holst, a columnist for PC Professional magazine in the early 1990's.

Holst wanted to demonstrate how susceptible people were to accepting as fact any statement they read on the internet or in their email. To illustrate this, she authored a list of "facts" and statistics, including a tidbit she found in an old text on insect folklore: the average person swallows 8 spiders per year. As Holst predicted, the statement was readily accepted as fact and quickly spread around the internet.

But is there any truth to the urban legend? Is it possible for us to swallow spiders while sleeping?

You can rest peacefully, because the chances of your swallowing a spider while you are asleep are almost none. And I only say almost none because nothing is impossible, I suppose. Not a single study has been done to date to quantify the spiders people swallow while sleeping. Why aren't scientists studying this phenomenon? Because it just doesn't happen!

In order to swallow a spider in your sleep, a number of unlikely coincidences would all have to occur in sequence.

You'd have to be sleeping with your mouth pretty wide open. If a spider crawled on your face and over your lips, you'd likely feel it, so a spider would have to approach you by descending from the ceiling above you on a silk thread. The spider would have to hit the target – your mouth - dead center to avoid tickling your lips.

And if it landed on your tongue, a highly-sensitive surface, you would feel it for sure. So the spider would have to land at the back of your throat without touching anything on the way in. And then you'd have to swallow.

But the real bottom line is this: spiders aren't going to voluntarily approach the mouth of a large predator. That's how a spider sees us, after all, as big, warm-blooded, threatening creatures that might eat them. What motivation would a spider have for crawling into your mouth?