Years ago when the median age of kids at our house was still in the single digits, I recall my son leaning in to whisper in my ear. 

"Achoooo!" He spluttered before returning to actual words. 

"God bless you," the reflex came before I could review it. I was of course the one in need of blessings, having just received a point blank blast of germs inserted in my middle ear. He had meant no harm, though. Nasal expulsions often arrive without preamble. 

"God bless you" is a common comeback for sneezes. Many people say it, with as little cognition as the sneezer. It's simply what you say. The habit is as entrenched as a smile after a joke. 

The practice began with sincere intentions however, back when people put more stock in evil spirits slipping into open mouths for devious purposes. The tradition circles the globe, coming out as "grow big" in Russia or "may you live 100 years" in the case of a Chinese sneeze. 

It would be hard to calculate the effects worldwide in terms of longevity and robust health. 

Recently I have begun a reflexive response to critical thoughts about certain people. My head starts whining about their ineptitude or annoying behavior and I say "bless you".  Out loud. If anyone planted themselves outside my sewing room they might be thrilled to hear how many people I confer good will on in the making of a single quilt. Or horrified. 

It catches the negativity as neatly as a handkerchief and instead of complaining I wish them well. 

It would be fascinating to try to measure the long term effects on people who otherwise bother me.