|Be a Blessing|
I recall someone sneezing. I did not say anything. That person immediately turned to me and said, "You did not say God Bless me." So I said it to appease them at the time. After I thought about it, I still wondered why people say it particularly after someone sneezes. I wanted to know what the significance was of is this, particularly at the time after a sneeze.
According to en.wikipedia.org., In the hope of fighting off the Bubonic Plague, Pope Gregory 1 in AD 590 ordered unending prayer and parades of chanters through the streets. Sneezing was thought to be early symptoms of the plague; it was thought that saying "God Bless You" would stop the disease.