text: Yes, postnasal drip can cause bad breath. \n\nI would first recommend an over-the-counter saline solution or an antihistamine (if your postnasal drip is caused by allergies). \n\nIf this condition continues for a prolonged period, you should see a doctor. This could be a sign of a bacterial sinus infection. In this case, a doctor could easily prescribe antibiotics to alleviate the problem.