Chinese medicine says that water is Yin, fire is Yang, the body to maintain health, we must achieve a balance of Yin and Yang. The body’s fluids, essence and blood all belong to the “yin” category. Therefore, the most distinctive feature of people with Yin deficiency is the lack of water, that is, the deficiency of Yin fluids such as fluid or essence and blood in the body. We all know that in nature, the sun provides energy, and water is the material basis for nourishing and moistening the world. Without water, rivers will dry up, ships will not run properly, the surrounding land will dry up and crack, and flowers and trees will wither and die. The human body is a small nature, if a person does not eat, he can live 7 to 10 days, but if you do not drink water, about 3 days can not live. Because the main component of the human body is water, if the body is lack of water, you say how serious this matter? Yin deficiency in the body lack of water will appear dry mouth, dry lips, dry skin, dry stools and other “loss of moisture” symptoms. “One yin and one yang is called the Tao”. Under normal circumstances, the ratio of yin and yang should be harmonious and stable, if the substance belonging to “yin” is less, the part belonging to “yang” will appear relatively strong, and there will be a phenomenon of internal disturbance of false fire. This is why Yin deficiency can not control fire, fire is afraid of heat, often the palms and feet are hot, sweating, sudden cold and heat are easy to blush; this is why people with Yin deficiency like winter and do not like summer, their body itself is hot. Good movement, cheerful and outgoing personality; temperament then seems impatient, which is why some thin people often get angry; such people look healthy and energetic, but in fact are already in a deficient, deficient state and can not afford to be repeatedly tossed. People with insufficient yin energy will have low functions of “cooling”, “moistening”, and “quieting”, and will clinically show symptoms such as heat in the palms of the hands and feet, redness in the cheekbones, dryness in the mouth and throat, dryness in the stool, and impatience. The clinical symptoms include heat in the palms and feet, redness in the cheekbones, dryness in the mouth and throat, dryness in the stool, and impatience. Specifically, there are heart, lung, stomach, liver, and kidney yin deficiencies, and the signs can be identified by medicine.