Why sneezes can’t pass without comment, as other involuntary expulsions of air manage to do, is beyond me. But I habitually observe the niceties even though I’ve never been comfortable with them.
I was raised to say, “God bless you” but since I doubt God has anything to do with sneezes or their remedies, I don’t say it anymore. For a while I would say “Gezundheit!” a puzzling invocation of German (a British friend took me to task for that once). Since marrying an Argentinian, I’ve been saying, “Salud!” though it’s not always understood by English speakers. I like it because you can say, “Dinero!” and, “Amor!” for the second and third sneezes respectively.
In trying to invent a suitable sneeze pleasantry I came up with one so universally offensive that from now on if you sneeze and I don’t say anything, it’s because I’m refraining from saying “Sneezus Christ!”