[walkswithwater]

I assume you mean you have an ulcer inside your mouth? If so, you will not be infected by anything from the listerine itself. If you have an ulcer inside your mouth though you should probably abstain from painting as it could potentially be an entry way for HIV infection. Highly unlikely, as HIV is very very very hard (maybe even impossible) to transmit through oral sex (especially from woman to man), but better safe than getting struck by lightning.