A 2008 study in the journal Archives of Oral Biology shows that during your period week and your premenstrual week your mouth has a higher concentration of volatile sulfur compounds–the stinky stuff produced by microorganisms that give you bad breath.
The problem is that low estrogen on these days reduces your mouth’s production of saliva, which means it’s less effective at naturally washing away these foul-smelling substances.
Luckily, keeping your breath fresh is easy: Simply brush your teeth and tongue more often on these days, floss regularly and use an alcohol-free mouth rinse (ones with alcohol lead to dryer conditions in your mouth, which can actually worsen the odor problem).
If those aren’t handy, studies show that sipping unsweetened green tea or black tea can freshen breath by killing the stench-causing microorganisms. And, even drinking plain ol’ tap water can help by simply rinsing away the malodorous compounds.