I italicize foreign words. Typically in dialogue. But I have a strange situation.
I specify the people are talking in Italian, but I write it in English, as in:
"May I join you?" Boyd asked in Italian which is what he spoke all the time since arriving.
And from that point on, even though everyone is speaking Italian, I write it in English. The reader simply knows they're talking in Italian. But later, there's a scene where they're speaking Italian (which I write in English) but use an English word. So do I italicize the word spoken in English? As in:
"His name is Regalo."
"Regalo? That means gift in Italian."
"Yes, he was a gift from God."