Mouthwash on a canker sore?

I seriously just had a canker sore last week on the opposite side of my mouth, and now it's back but on the other side. Anyway, to treat my last canker sore I dipped Q-tips in mouthwash and applied it to my sore. It seems to have worked very well. It relieved my pain and it healed it pretty fast. I've heard there are some harmful things in mouthwash, though. Could this method be bad for me, or could it hurt me in any way?