There are two reasons for yellow tongue coating, one is caused by poor oral hygiene, and the other is caused by fire in the body. People who have not brushed and rinsed their teeth seriously for a long time and have never gone to the hospital to have their teeth cleaned, this kind of people will have a lot of food debris and bacteria stored on the surface of their tongue, which will make the tongue moss yellow and thick, and it will be corrupted to produce a foul odor, resulting in halitosis. When the body is on fire, the phenomenon of yellow tongue coating will also occur, mainly in the crowd of people with strong stomach fire, strong stomach fire due to eat sweet, thick and greasy food, eat too much at every meal, and after the meal and did not carry out a moderate amount of exercise, which will result in the accumulation of food in the stomach, so that the stomach fire rises to lead to the yellowing of the tongue coating. If the patient himself has gastrointestinal digestive system diseases, such as suffering from gastric ulcer, gastric dyskinesia, chronic gastritis and other diseases, will also cause the accumulation of food in the stomach for a long time, leading to the phenomenon of yellow tongue coating.