Ideally (le-chatchila<\/i>), one should not wash one\u2019s mouth on the minor fasts, because there is concern that one might swallow drops of water.\u00a0 However, one who detects that his breath smells bad may wash out his mouth, because he has no intention to drink, only to clean his mouth.\u00a0 Still, he should be very careful not to swallow any water.\u00a0 One may use toothpaste in order to clean out his mouth thoroughly and remove a bad smell, if not doing so causes him distress.<\/p>\n
Tish\u2019a B\u2019Av is a stricter fast, which entails a prohibition against washing oneself. \u00a0Therefore, one should act more stringently and, unless it is very necessary, not rinse his mouth.\u00a0 Only someone who would be greatly distressed may wash out his mouth and brush his teeth, without toothpaste, even on Tish\u2019a B\u2019Av.\u00a0 On Yom Kippur, however, when one must fast according to Torah law, one should not be lenient.[6]<\/a><\/sup><\/p>\n