it's bad if you swallow it, lol, but other than that i have never heard of health problems from using mouthwash. too much might erode your teeth or cause gum pain, but it's easy enough to use a normal amount. personally i hate mouthwash, it hurts my mouth, but i use a toothpaste that contains neem which is like a natural mouthwash. my dental hygienist praises my mouth care and she thinks i use mouthwash.
I agree with both of them, Listerine is very effective but don't swallow it, I accidentally swallowed some last week and I had the taste in the back of my throat all day, the taste reminds me of Vic's Vapor Rub and that is just disgusting.
Listerine is everyone's favorite and does the job fine but can be too harsh because it contains alcohol and other chemicals which may kill off too many of your natural oral microbes. If this worries you, there are herbal mouth wash products that work just as well.
There have been a few hypotheses about mouthwashes causing oral cancers, but I don't think any have proper studies have confirmed it as of yet.
