Prosit is the standard Swedish response when someone sneezes.
It comes from the Latin word prosit, which literally means something like 'may it be good', from the verb prosum. You can roughly translate it as 'bless you'.
But why do we bless our sneezing friends and co-workers in the first place?
There are several different theories and it's impossible to know for sure, but some say it's because sneezes were thought to be due to interference from good or evil spirits, so a blessing was intended to ward off potentially evil spirits.
Another theory goes that centuries ago, people believed your heart stopped momentarily when you sneezed, while others still say that the expression originated during the plague, when people blessed sneezing friends in a bid to ward off the mysterious sickness. Whatever the answer, most Swedes will respond to a sneeze with a thoughtful prosit – and it's the same in Danish and Norwegian, too.
In many cultures, people respond to sneezes by either saying 'bless you' or 'good health'. In German, for example, the usual response to sneezing is Gesundheit! (literally 'health' with the understood meaning of 'I wish you good health') while Prost! also deriving from Latin prosit is used as a toast when drinking.
The late Swedish etiquette expert Magdalena Ribbing noted that it is polite to say prosit the first time someone sneezes, but that if they're caught in a sneezing attack, you don't need to keep repeating it. Beware though: Swedish folklore dictates that each time you say tack (thank you) in response to prosit, a gnome will die.
Achoo! Bless you!
På svenska brukar vi säga 'prosit' när någon nyser
In Swedish we usually say 'prosit' when someone sneezes