Rachel hates spiders. This situation was not improved when an East African jumping spider bit her last year. Even though Rachel knows all of the logical reasons why she should like spiders, they really creep her out. And Aaron had a horrible experience with a brown recluse spider bite on the middle of his forehead (which made his brother call him ‘the unicorn’). So the thought that we are routinely swallowing spiders in our sleep is incredibly freaky to both of us. You can imagine that someone may have first told someone like Rachel that they were swallowing spiders because they wanted to scare them, and the thought was so creepy that it stuck around. A 1954 book about insect folklore contained this myth, and most versions that are passed around imply that you are swallowing these spiders while you sleep. In 1993, a magazine article described this swallowing spiders idea as a myth, ‘a ridiculous belief of the sort that someone would actually believe’. And, in classic myth-spinning form, now people quote this article as a source documenting that people actually do swallow spiders every year (even though this is the exact opposite of what the author was saying).
How do we know that the average person is not swallowing eight spiders a year? Can we prove that this does not happen? No. There are no studies to prove that this does not happen, but there are also no studies to prove that this does happen. We could not find any studies documenting any instances of people swallowing live spiders accidentally. And without any science or evidence, there is no reason to believe that this is actually happening. Furthermore, there are a lot of reasons why it is virtually impossible that people are swallowing so many spiders.
We’ll be the first to admit that we are ‘people’ doctors and not experts on spiders. Therefore we must turn to ‘spider’ experts, such as the frighteningly dedicated aficionados at www.spiderzrule.com. (This site must be seen to be believed.) Why don’t we routinely swallow spiders in our sleep? First of all, most people roll around in their sleep. This rolling around would probably scare the spiders from wandering anywhere close to your face. Second, you would need to have your mouth open, and not everyone keeps theirs open while they sleep. Third, experts tell us that spiders, like other arthropods, instinctively flee from open, breathing mouths. This makes sense – if you are an arthropod, unless you are suicidal, you are programmed to try to avoid things that might eat you. Finally, the spider would have to walk into your mouth and stay there in such a way that your swallowing reflex was triggered. We do not automatically swallow every time something goes into our mouths. So the chance that all of these things would happen together – that there would be a wandering, potentially suicidal spider in close vicinity to your mouth and that they would actually wander in to the wet, dark, breathing space and trigger your swallowing reflex – is really incredibly small.
Still, some will claim that a spider could fall into your mouth. What if it was hanging from the ceiling just above your mouth? The odds of this happening are also incredibly small. Your mouth is a relatively small target for a spider to hit randomly. And before you start worrying that eight spiders are going into your stomach every year through your nose, it’s even more unlikely that you would swallow them this way than if they actively chose to crawl into your mouth. Your nostrils are (we hope) even smaller than your mouth, and thus an even smaller target for the spiders to hit. The most likely scenario if a spider actually went into your nose is that you would sneeze it out. The sneeze reflex is very sensitive and recognizes when even a small piece of dust gets in the nose.
It is possible that you have swallowed a spider, perhaps even more than one. But it is incredibly unlikely that you have swallowed eight in the last year. Or that enough people are swallowing spiders that each person would average eight (or any significant number) in a year. It’s a myth all around.