The origin of the “bless you” tradition is not entirely clear. The urban legend experts at Snopes.com list an impressive number of possibilities. One involves the (hopefully) mistaken belief that a human’s soul might escape through a sneeze. Saying “God bless you” wards off Satan while the soul is temporarily vulnerable. I’ve also heard that it was thought, in Biblical times, that a sneeze was an attempt to rid the body of a demon.
Another story veers toward the medical. Once upon an unenlightened time, people believed that the heart stopped during a sneeze. A hearty “God bless you” set the ol’ ticker back in motion. Keep in mind these were the days before defibrillators and HMOs.
Interesting, but the most popular theory comes from the Middle Ages. During the bubonic plague, a sneeze was believed to be a sign of impending death. “God bless you” was “a way of commending his soul to the care of God.” The phrase may have also come in handy to protect oneself if someone nearby sneezed.
Today, “bless you” is more a sign of good manners than a shield against death. If only folks were as courteous about other involuntary bodily functions…