good question, Many people have become accustomed to saying "bless you" or "gesundheit" when someone sneezes. No one says anything when someone coughs, blows their nose or burps, so why do sneezes get special treatment? What do those phrases actually mean, anyway?
Wishing someone well after they sneeze probably originated thousands of years ago. The Romans would say "Jupiter preserve you" or "Salve," which meant "good health to you," and the Greeks would wish each other "long life." The phrase "God bless you" is attributed to Pope Gregory the Great, who uttered it in the sixth century during a bubonic plague epidemic (sneezing is an obvious symptom of one form of the plague)
We now know that sneezing is a reflex action and is most often the sign of something relatively benign, such as a cold or allergy. A sneeze also can be provoked by being outside in the sunlight or from smelling a strong odor. Still, we persist in the custom of saying "bless you" or "gesundheit," mainly out of habit and common courtesy.
The exact reason is lost to antiquity, but there are many possible reasons put forth. Some believed that when you sneeze, your soul tries to escape your body (same with yawning). Some believed a sneeze was a prophetic sign that something bad was about to happen. Some believed that a sneeze meant someone was talking about you. In any case, it was bad, so blessing someone is probably a positive way of dealing with impending doom.
Oh yeah, your heart does not stop when you sneeze, it MIGHT skip a beat, but doesn NOT stop...... heres a couple links.......