Does the sting of mouthwash mean it's working?

Not really: Not all mouth washes sting, but you do notice the alcohol that causes that burn and that does help to kill some of the bacteria. It should be working no matter what it tastes like, but you can not tell how good. Some work well and others not so well. Nothing replaces brushing and flossing though.

Mouthwash sting: Not necessarily. Have you tried a mouthwash without alcohol? This might be best for you. If you have a rope type saliva, it may be tissue sloffing off, which is not good. Switch to another brand and see if the tissues feel better.