halacha - Mouthwash on a public fast day?

Is it permitted to use mouthwash on a public fast day? Would a sensitive mouth, due to medical reasons be a good reason to be lenient?

(I can see it being less problematic than brushing one's teeth, because there's no fresh water being used, only the chemical mix that is mouthwash; that's not something you'd drink.)

Answer

Per Mishna Berura Orach Chaim 567:3:11 if a person is bothered by the lack of brushing their teeth or the smell/taste in their mouth, they are permitted to rinse their mouth on public fasts, however one should tip their head forward in order that it should not reach their throat.