maybe he's used to being around women and their hygienic needs aren't a big deal.Some women are open about it, especially if they have drastic mood changes, decrease energy or migraines. I know two of my coworkers cycles because they always call off with migraines. If they are roommates it's possible she just told him. Some people think of tampons like they would toilet paper. "Hey I'm on my cycle. Can you pick up some tampons from the store? I don't feel like going out, my cramps are bad. Here's five bucks. Get some Tylenol too".