Is any urban legend more shudder inducing than the one about humans swallowing an average of eight spiders a year in their sleep? The idea of unwittingly ingesting eight-legged interlopers is viscerally horrifying.
But is there any truth to this creepy notion? We spoke to experts on both sides of the science here—human and arachnid—in hopes of putting this claim to bed.
Spider behavior makes this incredibly unlikely.
“The idea that spiders crawl into people's mouths while they sleep, let alone that you swallow a certain number of spiders a year—5, 8, 10—is a myth,” Michael Skvarla, Ph.D., insect identifier and extension educator in the Department of Entomology at Penn State University, tells SELF.
Turns out spiders tend to be more homebodies than adventurers. Many of the species that often live in houses, like longbodied cellar spiders and hacklemesh weavers, spin webs that they are “reluctant to leave,” Skvarla says. (The exception is typically males who are ready to mate, but their explorations are often brief.)
While there are some species of home-dwelling spiders that hunt their prey instead of catching it in webs, like agrarian sac spiders and parson spiders, Skvarla says they usually prefer to shack up in undisturbed spaces like closets or basements.
“A bed is not an appealing place to be,” Skvarla explains. “There are not typically insects in and around a bed to attract spiders that are searching for prey.” (If there are, you’ve got bigger problems.) Basically, if a spider knows its main interest—food—is not likely to be present somewhere, it typically won’t care to explore that area at all. Relatable. And also great when that area is your bed.
While a hunting spider could theoretically venture into an area where there is little or no prey, like your bed, Skvarla says spiders generally confine their hunting grounds to the areas their spidey senses tell them prey is more prevalent.
So, how do hunting spiders know where their next meal might be? Arachnids detect the presence of their prey in various ways depending on the species, Skvarla explains, from eyesight to chemical cues. But one major way spiders interpret the world is through vibration receptors on their legs. As Skvarla explains, the booming vibrations you produce as you sleep (rolling over, shifting slightly, even breathing) are going to be a huge turnoff to spiders. No offense.
Human biology also makes swallowing a spider unlikely.
In the improbable event that a lost and confused or bold and brazen spider did decide to waltz in the direction of your mouth hole, it’s doubtful that you would end up swallowing it.
“Knowing the anatomy of our mouths and our throats and the physiology of how we sleep, it's nearly impossible,” Erich Voigt, M.D., chief of general/sleep otolaryngology at NYU Langone Health, tells SELF.
Of course, never say never. If you got really, really unlucky and every single detail lined up perfectly, it’s possible that you could swallow a spider. Wilder things have happened, and certain factors might make this more probable, like if you live in a home with a ton of spiders or are camping in a place that spiders love. Otherwise, the chances of this chain of events unfolding perfectly enough for you to swallow a spider—especially for you to swallow eight over your lifetime—are incredibly low.
The first line of defense is your sense of touch. If a spider were to make its way onto your face, you might feel it and brush it off, even in your sleep.
“We still maintain sensation [in] our faces and necks when sleeping and can potentially feel something crawling on our faces,” Jason Abramowitz, M.D., an ear, nose, and throat physician with ENT and Allergy Associates, tells SELF.
Skvarla has been there: “I experienced this when, as a college student, I slept on a mattress directly on the floor and slapped a spider on my face in my sleep.”
Let’s say a particularly stealthy spider made its way onto your face and you didn’t feel it. Your mouth would probably be closed, Dr. Abramowitz says, so problem solved there. If you sleep with your mouth open, you’re likely snoring, Dr. Abramowitz says—producing vibrations in the mouth and throat that, as we discussed, would probably scare a spider in your vicinity.
Now let’s suppose you happen to be a delicate enough snorer that it wouldn’t frighten a spider, and the little guy does decide to go spelunking in the dark abyss that is your mouth. It’s still probably not going to make it far, Dr. Voigt says.
One line of defense is that handy old gag reflex, which is meant to expel any foreign body that could cause you to choke, Dr. Voigt explains. This automatic contraction kicks in if something reaches the back of your throat at any point when you’re not naturally swallowing. Even if a spider didn’t trigger your gag reflex and made it into your throat, you might begin to cough as a means of ejecting the critter.
Then, if a wily spider slipped past your throat, your esophagus would likely put a stop to any more arachnid nonsense. Your esophagus is the tube that connects your throat to your stomach. It has a ring called an esophageal sphincter at either end. These sphincters are normally closed unless a chain of physiological processes signals that it’s time for them to open to allow food or beverages to pass.
Chewing and swallowing prompt your upper esophageal sphincter to open, and since you wouldn’t be doing that if a spider crawled into your mouth, this sphincter would typically stay closed. But (and this is a big but), if you happened to be in the process of swallowing as you slept due to saliva buildup, and a spider were waiting patiently for admission to your stomach, you could theoretically gulp it down. But do you see how many steps would have to line up perfectly for this to happen?
Thank goodness, you can discount this spider-swallowing myth.
Even if it happens once, you’d basically need to try to make it happen seven more times to hit that lifetime count of eight. And, honestly, even if it did happen, swallowing a spider as you sleep seems way less scary than waking up with a cockroach in your ear.