Why do people say “God Bless You” when you sneeze?
In the medieval time, people thought that when you sneeze, your soul leaves your body through the nose and you are dead for that millisecond of time. This happens within 500th of a second. Your eyes get close, your heart best stops, your body gets sucked and start getting goose bumps all over and you really can not do anything.
There is a saying that devil/demon always sleeps on your nose and always finds a way to get inside your body. Now, within that meantime, when he finds your body without a soul, he tries to get inside before your own soul gets inside your body.
But if somebody says “God Bless You”, they protect you from the bad spirits or that devil from entering and possessing your body and your soul gets a chance to get back in it.