There’s a “fact” that goes around that claims that every person swallows a few spiders in their sleep every year. This “fact” is purely fictitious, and was actually made on purpose by someone who wanted to prove how easy it was to create an urban legend. It’s also highly unlikely that its ever happen to you once as spiders usually avoid humans as things like snoring and heart-beats would most likely scare any spider and cause them to go elsewhere.