Drinking milk mouth especially stinky may be the mouth milk residue and gastrointestinal tract dysfunction caused by the following: 1. Milk residue in the mouth: Milk is a rich protein, calcium and other nutrients in the drink, after drinking milk if you do not clean up the mouth in time, it will cause milk residue in the mouth, the residual milk for the anaerobic bacteria in the mouth to provide a good living environment, the breeding of bacteria will decompose proteins, produce gas containing sulfide odor, which is the cause of the mouth odor. 2. Gastrointestinal tract dysfunction: a one-time consumption of a large number of milk can not be digested and absorbed in a timely manner, the anaerobic bacteria in the gastrointestinal tract will decompose the milk, resulting in the smell of corruption, which produces the phenomenon of bad breath. To prevent bad breath after drinking milk, you can rinse your mouth with water or drink a small glass of warm water to clear the milk residue in your mouth after drinking milk. If the bad breath is severe or if you clearly have an oral disease, you should seek medical attention and treatment.