A bad taste in the mouth with or without food is often a message that signals a disease. Bitterness in the mouth is common in acute inflammatory diseases, especially in liver and biliary diseases, which is mainly related to the metabolic malfunction of bile. According to traditional Chinese medicine, bitterness in the mouth is mostly due to heat in the liver and gallbladder. Sweet mouth is mostly seen in the digestive system dysfunction. This is because the dysfunction of the digestive system can cause abnormal secretion of various digestive enzymes, stimulating the taste buds on the tongue and feeling sweet. In addition, diabetic patients due to the increase in blood sugar, saliva sugar also increased, also sweet in the mouth. Light mouth is mostly seen in digestive system diseases, endocrine diseases and malnutrition, vitamin and trace element zinc deficiency, egg quality and calorie intake is not enough disease. All of these diseases can make the tongue taste buds become less sensitive and the mouth is light and tasteless. In addition, the elderly taste buds aging will also produce this feeling, but not disease. Salty mouth is common in diseases such as mouth ulcers, chronic nephritis and pharyngitis, and kidney function impairment. This disease is common in the kidney yin deficiency, the ancestral medicine has “salty for the kidney taste”, that is, for this reason. Modern medical research proves that the above-mentioned diseases, its saliva in potassium, sodium, calcium, magnesium content increased greatly, alkaline. Spicy mouth is common in hypertension, menopause syndrome and neurosis and long-term low fever and other diseases. It is worth mentioning that spicy taste is not a single sensation, but a combination of heat, pain and salty sensation, therefore, patients with spicy mouth have high tongue temperature and the tongue mucosa is more sensitive to the pain of salty taste. Mouth acidity is common in diseases such as gastritis and peptic ulcer, which is related to excess secretion of stomach acid.