Yin deficiency fever, a disease name. Deficiency fever caused by the loss of essence, blood, body fluids, etc. See "Danxi Xinfa·Fever". "Zhengzhi Huibu·Yin deficiency fever" says: "If you work hard and like sex, your true yin will be injured. Once the yin blood is damaged, the yang qi will be strong, and the fever will not stop, and it will be worse in the evening. Or if you eat and drink normally, your head will swell from time to time, your pulse will be strong and weak, and your tongue will be large and red, then it is yin deficiency." According to traditional Chinese medicine, the human body is composed of yin and yang. Yin refers to the material basis of the human body, such as essence, blood, body fluids, etc., and yang refers to the various functional activities of the human body. Under normal circumstances, yin and yang depend on each other and maintain a dynamic balance. If this balance of yin and yang is destroyed, one side of yin and yang becomes stronger or weaker, and people will get sick. The physical characteristics of children are that yin and yang are relatively insufficient. Under the influence of some pathogenic factors, they are prone to exogenous febrile diseases. Children with high fever or long-term fever can often damage body fluids, thus leading to yin deficiency fever.