Sneeze - "Bless You!"
Sneezing seems to carry with it many superstitions. In Ancient Greece, sneezes were believed to be prophetic signs from the gods. In Chinese culture, a sneeze is perceived as a sign that someone was talking about the sneezer at that very moment. What does Judaism have to say?
The Aish Rabbi Replies:
Genesis 48:1 says that Jacob became ill. Why does the Torah need to teach this? Because until that time, no person had ever experienced illness as a sign of pending death. Rather someone would be walking along one day, they'd sneeze, and die instantly. Jacob, however, prayed to God for a period of infirmity prior to death, as a warning sign that it is time to make final preparations.
Why did the "sneeze" cause death? Because in creating humanity, "God blew into Adam's nostrils the soul of life" (Genesis 2:7). Therefore when a person sneezed, the soul would exit from the same place it had originally entered - hence death. (see Radal)
We find an application of this in the Bible, where the prophet Elisha was able to revive a child who had died. "The boy sneezed seven times, and the boy opened his eyes." (2-Kings 4:32-35)
Interestingly, in even more recent times - before the advent of antibiotics - a sneeze was a sign of grave danger. Sneezing was a sign that the person had a cold. If the cold should turn into pneumonia (which it often did), then for all intents and purposes the person had just a few more days to live.
Today, when a person sneezes, we have the custom of saying, "God bless you" (or something similar; in Hebrew we say "labriut" - to your health) since sneezing was once a sign of mortal danger.
By the way, the Code of Jewish Law (OC 103:3) says that sneezing during the middle of the Amidah prayer is a good omen. To learn more, see Pirkei d'Rebbe Eliezer 52; Talmud - Baba Metzia 87a, Sanhedrin 107b, Brachot 53a.
And God bless you!