Question

Can you use italics for your character's thoughts in a narrative first-person essay?

Answer 1

Answer: If it is internal dialogue (your thoughts) yes.

Explanation:

You can, in general.  Each instructor may rely on her own preference, but there is no standing rule against using italics, and I think it helps the reader separate or differentiate between past and present. For external dialogue use quotation marks, for internal, use italics.