This is a common belief; but I believe it is an urban legend.
"most people breathe while they sleep ... and spiders, like virtually all arthropods, flee from breath. After all, there are lots of vertebrates that EAT arthropods, and if you're an arthropod and something is breathing on you, it's not a good idea to stick around."
The Straight Dope: Does the average person consume four spiders per year in his sleep?
I think this is a rediculous myth. First of all, many people would wake up if anything was on them or crawling into their mouth. Also, many people sleep with their mouth closed, making this impossible. Why would people randomly have spiders around their house if you don't have a bug problem? I wouldn't worry about this. I doubt there is any truth in it.
Not everyone would wake up because some people are heavy sleepers.
my sister told me a bunch of things first of all she told me if you eat corn or peanuts you can see it in your poop. Second of all she said when you sleep with your mouth open spiders crawl in your mouth. They could unless you sleep with your mouth open spiders can. But if you don't spiders don't crawl in your mouth
Other people asked questions on various topics, and are still waiting for answer. Would be great if you can take a sec and answer them