When to italicize alias?

I have a doubt. I have seen that sometimes the word alias is
italicized and sometimes it is not italicized. Is there any reason
behind this?

Thank you.

Answer

Do not italicize alias when you use it to mean an assumed name.
“The spy used the alias of George Brown on his mission.” On the
other hand, italicize alias when you use it to mean “otherwise
known as”: John Smith alias Machine Gun Johnny (literally “John
Smith, otherwise known as Machine Gun Johnny”).