Yellow tongue coating is mainly caused by fire in the body, and is commonly found in people with strong stomach fire or strong liver fire. Stomach fire is mainly due to the long-term preference to eat greasy, indigestible food, or the patient itself has gastric ulcer, indigestion and other gastrointestinal system diseases, due to the accumulation of food, food in the stomach for too long, resulting in stomach fire, the fire in the stomach rose to the inside of the mouth will cause the yellow tongue moss, oral odor. Liver fire is common due to stressful life and work, or long-term anxiety and tension, or the patient is irritable or sulking for a long time, which can lead to stagnation of liver and gallbladder gas, causing liver fire, and the fire rising to the mouth will also cause a series of symptoms such as red and swollen gums, thick yellow tongue coating and bad breath.