Thick tongue, mainly thick and greasy tongue coating, is generally caused by the accumulation of phlegm and dampness in the body. Phlegm-dampness is a watery substance that is sticky in nature, just like paste or glue, and has a white or yellow color, which requires specific analysis of the problem. First of all, Chinese medicine believes that the function of the spleen is to transport and transform the body’s watery fluids into normal absorbable components through the spleen’s transport and transformation. When the function of the spleen is dysfunctional and the function of transporting and transforming water fluids decreases, the fluids will coalesce and concentrate, just like the water in a river. When the river is flowing at a faster rate, the water is clear, while when the flow rate decreases, the water becomes turbid or even turns into silt. This is what is meant by “flowing water does not rot, the household pivot is not worm-eaten”. In the human body, phlegm and dampness will be formed, and the tongue will appear thick and greasy on the tongue. At the same time, the function of the stomach is to digest food and drink, the dregs and other metabolites to the intestinal tract excretion, when this function of the stomach decreases, so that the peristaltic emptying ability of the stomach, metabolites are easy to accumulate in the gastrointestinal tract, the formation of dry damp, food accumulation or damp heat. The gastrointestinal tract is blocked, just like the sewer is not working, turbidity, odor will be retrograde and upward, the tongue will be thick and greasy. Secondly, according to Chinese medicine, “the lung is a storage vessel for phlegm”, the lung is like a container, the phlegm and dampness formed by the dysfunction of the spleen and stomach can easily be stored in this container of the lung. The common diseases such as chronic bronchitis, asthma and bronchial dilatation will be aggravated acutely after a cold, and the external sensation will trigger the internal phlegm-dampness, and the tongue will appear thick or greasy. If the wind-cold disease is felt, the tongue is thick and white. If one feels wind-heat, the tongue will be thick and greasy or yellow. In addition, if a person has long-term insomnia, anxiety, irritability, etc., the emotion turns into fire, or if there is yin deficiency and fire, it will also cause heat to deplete the body’s fluid and form water concentration to form phlegm and dampness, and the tongue moss will appear thick or greasy, because there is heat and usually there is also a red tongue performance. These are the common causes of thick tongue coating.