I got a rash out of nowhere a few days ago, haven't been outside or anything. The next day I woke up with a...?

It could be. A girl in my class has mono but she doesn't seem all to sick however she sees the doctor all the time so that might be why. I had hives all over my body after eating Chinese food with my dad. I assumed i was allergic to MSG but being in denial i tried eating the same things as i did the last time at the same restaurant but nothing happened. So it could just be something normal like a weird flu, normally the body fights off infection like that, but i would still see a doctor in case it is mono.