In past times it was commonly believed that when a person sneezed, a demon was expelled from the body. I don't even know how I know that.
Sneezing was thought to be an early symptom of the plague, 'God Bless You' was a sort of shield against evil. Sneezing was also though to be a way of expelling the Devil from your body, so 'God Bless You' was a natural response
You say it in response to someone sneezing, or in some cases, as a fervent thanks for something they did for you that helps you greatly.
because shes waiting for you to say bless you
The phrase was started by Pope Gregory the first, during the bubonic plague. The early symptoms were sneezing and he advised people that if they saw someone sneezing to say the words 'God bless you.' he actually said suck my balls
Most certainly not. Or you will die
What I found out, was that after sneezing, when somebody says "bless you", it clears all the negative spirits from your life, but if you say "thankyou" it lets them back in. Whether this is real or just a superstition is unknown.
A vos souhaits or A tes souhaits (Bless you) Pronounced: Ah vo soo-ay or Ah tay soo-ay
God can't sneeze, for he cannot be sick. He's perfect. If God were to choose to sneeze (sneezing is not always a symptom of an illness) and you were on hand to witness it, it would not be inappropriate to say "You bless You" which is a short way of saying "May you bless yourself".
No one really knows..... maybe people are just use to it. It was once believed that sneezing was something to do with being possessed by demons, so 'bless you' i.e.'God bless you', would help save you.
Better to say Bless You
For a long time it was superstitiously believed that a sneeze ejected a small part of the soul. "God Bless You" was meant to implore the Almighty to preserve the soul.
In short, no-one knows. A common story is that during the time of the bubonic plague (of which sneezing was an early symptom) people would say "bless you" in case the sneezer had the plague - the practise having started in 590 by Pope Gregory I. However, it's known that people have said "Bless-you" after a sneeze since at least 77AD, so the plague explanation seems unlikely.