When someone sneezes, you might say Bless you!, at least in English.
In Spanish, I discovered the other day, you say ¡Jesús!. A Welsh friend told me this, and another friend thought it sounded like the Welsh phrase Ga i sws? (May I have a kiss?).
In Welsh you might say Rhad arnat ti!/arnoch chi! (Bless you!), Bendith y Tad! (Blessing of the Father!) or Bendith y mamau! (Blessing of the mothers!).
In French you say À tes/vos souhaits ! (As you wish!).
In German you Gesundheit! (Health!)
What about in other languages?
Aqui (português do Brasil) se diz simplesmente “Saúde”!
In Danish we say “Prosit!” which is originally the 3rd person singular active present conjunctive of the latin verb ‘prosum’, “I benefit”. So “Prosit!” actually means “May it benefit (you)!”
The French also have a phrase said to someone who sneezes again after an “À tes/vos souhaits !”: “À tes/vos amours !” (“To your love affairs!”).
Wiktionary reports that “[s]aying bless you after a sneeze is not considered particularly religious” but “[s]ome speakers who are not comfortable saying bless you might instead use the German loanword gesundheit.” I always thought that gesundheit was simply an alternative American English expression instead of a way to avoid using a religious formula.
Source: https://en.wiktionary.org/wiki/bless_you
In Finnish we say Terveydeksi! (for your health). I don’t know how common it is today, I rarely hear it used.
In most Spanish-speaking regions, one absolutely does not say “Jesús”, but “salud” (which, of course, also means “health”). I’m a native Spanish speaker and, though I don’t have contact with a lot of other regions, so I can’t say how common it is, I’ve never heard anyone say “Jesús” when another person sneezes.
Swedish – Usch, han frös och han nös,
atschi, atschi, atschi, prosit!
Esperanto – Ho, li frostis kaj li ternis,
—- je via sano!
“Çok yaşa!” (means “Live long” in Turkish)
In Norwegian we say Prosit, just like danish and Swedish. In Northern Sámi it’s been borrowed as Rusit.
Russians (and some Ukrainians) may say “Bud-zdarova” which loosely translates as “Be well” or “may you be healthy” similar to the phrase for “Cheers” which is “Na-zdarovya” (to your health!)