There are various theories on why we say ‘Bless you!’ when someone sneezes.
Theory 1: Sneezing was a symptom of plague and ‘God bless you’ was a prayer to give one strength to fight this deadly disease.
Sneezing (because of chills) was one of the primary symptoms of the plague that affected Rome city in the year 590.
So, Pope Gregory-I felt ‘God bless you’ would be the right thing to say as it was a small, little prayer for someone who may be affected by the deadly disease.
So, he commanded Christians to respond to a sneeze with a blessing.
Some sources say it was the plague of the 14th century and not of the year 590, and that it was Pope Gregory VII and not Pope Gregory I, who commanded people to say the blessing.
‘God bless you’ eventually became ‘Bless you’ as it reduced religious implications (even atheists could say it).
It, then, got passed on from adults to children, who started seeing it as an etiquette: if we don’t say ‘Bless you’, the sneezer would feel we don’t care about their health.
While this is the most accepted theory, mentions of ‘Bless You’ as a reaction have been found to date back to 77 C.E., but no explanation for the same has been found.
Theory 2: Ancient belief that a sneeze might accidentally force out the spirit from the body unless God blessed you and prevented it from happening.
Theory 3: Sneezing was seen as a sign of a healthy body, and the Greeks and Romans expressed their good wishes to the sneezer by saying ‘live long’ or ‘May Jupiter bless you’.
Theory 4: We say ‘Bless you’ because your heart briefly stops beating when you sneeze, so people say it to ensure your heart continues beating.
But the stopping of the heartbeat has been found to be a myth – the heart doesn’t stop when we sneeze.
