Differentiation of Six Meridians first appeared in Treatise on Febrile Diseases, which was a dialectical method for treating exogenous diseases based on articles such as Su Wen Re Lun by Zhang Zhongjing, a physician in the Eastern Han Dynasty, and combined with the characteristics of typhoid spread.

Syndrome of six meridians is a reflection of pathological changes of meridians and viscera. Among them, the syndrome of Sanyang disease is based on the lesions of six fu organs; The syndrome of three yin diseases is based on the pathological changes of five internal organs.

The syndrome differentiation of exogenous diseases is based on six meridians (Taiyang meridian, Yangming meridian, Shaoyang meridian, Taiyin meridian, Shaoyin meridian and Jueyin meridian), which can be classified into six categories: Sanyang disease (Taiyin disease, Yangming disease and Shaoyang disease) and Sanyin disease (Taiyin disease, Shaoyin disease and Jueyin disease).

Anyone with strong disease resistance and high disease potential is the syndrome of Sanyang disease; The disease resistance is weakened and the disease potential is weak, which is the syndrome of three yin diseases.

Syndrome of six meridians is a reflection of pathological changes of meridians and viscera. Among them, the syndrome of Sanyang disease is based on the lesions of six fu organs; The syndrome of three yin diseases is based on the pathological changes of five internal organs. Therefore, the syndrome of six meridians basically summarizes the pathological changes of the twelve meridians. The application of syndrome differentiation of six meridians is not limited to the diagnosis and treatment of exogenous diseases, but also has guiding significance for the treatment of internal injuries and miscellaneous diseases.