Can someone help me with Italian citizenship?

It actually is not for me, but for a relative. He was born in the US, his father is Italian. If I remember correctly my relative did, and probably still does have an Italian passport. The thing is he is 18 now, and I want to check for him if he needs to apply to maintain his citizenship, or does he just get to keep it without doing anything? I hate for him to lose it, especially now with the EU passport, which could give him incredible opportunity in the future.

I know Italy is pretty lax about giving citizenship to Italians (meaning granting citizenship to people who were not previously citizens but have a parent or grandparent who was Italian) so maybe I am worried for nothing, and they simply don’t take away his right to be an Italian citizen as he becomes an adult.