Mouth acidity, Chinese medicine believes that dry heat is sour in the mouth, the spleen and stomach gas is weak and sour in the mouth, so the mouth acidity to spleen deficiency and liver fire is predominant, common in gastritis, peptic ulcer, related to excessive gastric acid, some people determine the saliva of patients with mouth acidity, which lactic acid, phosphatase, carbonic anhydrase content is higher than normal, the pH value is on the acidic reaction; mouth bitterness, clinical observation of mouth bitterness, mostly seen in liver and gallbladder heat evidence, intestinal and gastrointestinal heat evidence, etc.. In modern medicine, it is mostly the manifestation of acute inflammation, and liver and gallbladder diseases, which may be due to bile excretion malfunction, cancer patients feel bitter tongue even when eating sweet things due to elevated desire for sweet taste and reduced desire for bitter taste; bad breath, on the one hand, is due to bad teeth, which leads to food embedment and fermentation of food to produce bad smell, and the second reason is bad gastrointestinal, long-term acid reflux, which leads to bad breath.