If you are in the presence of someone who sneezes, it was an ancient custom to protect him/her/ from danger or illness by saying, "God bless you,".Roman citizens feared sneezing when a plague hit their city during the reign of Pope Gregory the Great. Since they regarded the sneeze as a sure sign of approaching sickness, Pope Gregory pioneered the use of the phrase "God bless you" to shield sneezers from any ill effects.