wow, you so do not have anything to worry about. mouthwash definitely won't hurt you.
when i was in high school this girl in one of my classes didn't have time to brush her teeth that morning, so she brought her full bottle of Listerine to band that morning. At first, she just swished it in the girls' bathroom and spat it out, but then she started to swish and swallow. We were like, "Jaret, what the hell are you doing? Don't you know how much alcohol is in mouthwash you idiot?"
Well, she went from swishing first to just plain drinking it down. By the time band was over she had polished of the entire ******* bottle and was drunker than a skunk.
Moral of the story: the only thing swallowing mouthwash (and cough syrup, for that matter) will do to you is get you sloshed from all the alcohol and looking like this http://www.healthboards.com/ubb/dizzy.gif