The practice of blessing someone after a sneeze is probably as old as the first century. The origin of the practice is most likely rooted in superstition: the belief that a sneeze is the body trying to rid itself of evil spirits, the thought that the heart stops beating when a person sneezes, or the fear that a sneeze somehow opens the body to evil spirits. In these cases, saying, “God bless you,” was a kind of protection or good luck charm that shielded the sneezer from being invaded by spirits or affected by evil. Other cultures have a similar response to sneezes, believing that a sneeze could signal ill health: they might say, “Salud” (Spanish for “health”) or “Gesundheit” (German for “health”) or “Sláinte” (Irish Gaelic for “good health”) or “Jeebo” (Bengali for “stay alive”).
During a plague that occurred in Italy in AD 590, sneezing was, or was thought to be, a sign that someone was getting sick with the plague. There is a legend/tradition that Pope Gregory I commanded that, any time a sneeze was heard, the sneezer was to be blessed by saying, “God bless you,” (and making the sign of the cross over his mouth) as protection against the plague. Again, there is no biblical validity to such superstition. At the same time, there is no biblical reason to believe it is sinful to bless someone after a sneeze—in fact, it might just be a good time to extend a kind word and say, “God bless you.”