Why do people say bless you after you sneeze?

There are two possible reasons for people's response to a sneeze. The first is that people used to believe that one's soul escapes from the body through the nose when they sneeze. Saying "bless you," was supposed to prevent the soul from leaving and being taken hold of by the devil. The other reason people say "bless you," is that people used to believe that the heart stopped when they sneezed. Saying "bless you," was a way of welcoming them back to life!