Unknown to many, bad breath, or halitosis, can originate from digestive issues in the colon. Constipation: backup leading to the decay of waste matter in the colon can cause an unpleasant odor to emanate from the mouth. Although bad breath is a common problem, no amount of oral hygiene or masking bad breath with mouth fresheners can completely eliminate this type of bad breath. Getting to the root cause of bad breath will provide a more permanent solution for this type of halitosis.