We Swallow Spiders in Our Sleep: Myth or Fact?

The chance of that happening is near zero

Common house spider on the floor in a home
CBCK-Christine / Getty Images

No matter what generation you grew up in, chances are you heard the rumor that we swallow a certain number of spiders each year as we sleep. The truth is that your chances of swallowing a spider while you're asleep are slim to none. 

Unlikely Sequence of Events

Not a single study has been done to quantify the number of spiders people swallow while sleeping. Scientists don't give this topic a moment's glance, however, because it's highly unlikely. You can rest peacefully because the chances of swallowing a spider while you are asleep are almost zero. The only reason researchers don't say the chances are zero is that little is impossible.

For you to unknowingly swallow a spider in your sleep, a number of unlikely occurrences would have to happen, in sequence:

  1. You would have to be sleeping with your mouth wide open. If a spider crawled onto your face and over your lips, you would likely feel it. So a spider would have to approach you by descending from the ceiling above you on a silk thread.
  2. The spider would have to hit the target—your mouth—dead center to avoid tickling your lips. If it landed on your tongue, a highly sensitive surface, you would certainly feel it.
  3. The spider would have to land at the back of your throat without touching anything on the way in.
  4. At the very moment the spider landed on your throat, you would have to swallow.

Fear of Humans

Spiders aren't going to voluntarily approach the mouth of a large predator. Spiders view humans as dangerous to their well-being. Sleeping humans are most likely viewed as terrifying.

A slumbering person breathes, has a beating heart, and perhaps snores, all of which create vibrations that warn spiders of imminent threats. We appear as big, warm-blooded, threatening creatures that might eat them on purpose.

We Might Eat Spiders While We're Awake

Even though the rumor about swallowing spiders in your sleep is untrue, that doesn't mean you don't accidentally eat spiders. Spider and insect parts make it into our food supply every day, and it's all FDA approved.

For example, according to the FDA, an average of 60 or more bug fragments are in each quarter pound of chocolate. Peanut butter has 30 or more insect fragments per quarter pound. Everything you eat likely has critter parts in it, but this is normal: It's generally impossible to avoid having these mini body parts in our food.

As it turns out, however, bits of arthropods in your food won't kill you and in fact can make you stronger. Protein and nutrient levels in some insects and arachnids match those found in chicken and fish.

Don' t Trust the Internet

To test her theory that people are susceptible to accepting as true anything they read online, Lisa Holst, a columnist for PC Professional in the 1990s, conducted an experiment. Holst wrote a list of fabricated "facts" and "statistics" including the folklore about the average person swallowing eight spiders per year and put it on the Internet.

As she hypothesized, the statement was readily accepted as fact and went viral.

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