tinyurl. com – READ the 10 Minute Bad Breath report NOW!!! Factors that affect the mouth and cause bad breath * Dental decay. * Gum disease. * Food stagnation between the teeth. * Dry mouth. * Excessive bacterial activity on the tongue, possibly due to postnasal drip (catarrh coming down the back of the throat from the sinuses and nasal passages). * Throat or tonsil infection. * Catarrh.