Objective

To explore the laws in syndrome differentiation of Taiyang disease and the prescriptions and herbs used in its treatment in Shanghan Lun (Treatise on Febrile Diseases).
Methods

The occurrence rates of main syndromes of Taiyang disease, and the usage frequency of the prescriptions and herbs in its treatment were calculated, and the laws in syndrome differentiation and herbal medication were analyzed by hierarchical clustering analysis.
Results

Fever and aversion to cold were found to be the main symptoms of Taiyang disease and usually accompanied with headache, absent sweating, neck stiff, floating and tight pulse, and body ache. The accompanying or aggravated symptoms could be classified into lung system syndrome with the manifestations of sweating and asthma, spleen-deficiency syndrome with the manifestations of gastric fullness and diarrhea, stomach syndrome with vomit and constipation. Guizhi decoction was the main prescription used in the treatment of Taiyang disease. Mahuang (Herba Ephedrae) matching Xingren (Semen Armeniacae), Dahuang (Radix et Rhizoma Rhei) matching Mangxiao (Natrii Sulfas), Baizhu (Rhizoma Atractylodis Macrocephalae) matching Fuling (Poria), Fuzi (Radix Aconiti Lateralis) matching Ganjiang (Rhizoma Zingiberis), Chaihu (Radix Bupleuri) matching Huangqin (Radix Scutellariae), Banxia (Rhizoma Pinelliae), and Renshen (Radix Ginseng) as the main compatibilities were used in treating lung diseases, stomach diseases, spleen-deficiency diseases, kidney-deficiency diseases and Shaoyang diseases respectively.
Conclusion

Exterior syndrome, as a common syndrome in Taiyang disease, is usually treated with Guizhi decoction. The change in syndromes from upper-energizer to lower-energizer in exterior disease can be found from the change of symptoms and the use of herbs. And the development from defending stage to qi stage in exterior disease can be found in the use of prescriptions in Shanghan Lun.

Key words: Shanghan Lun (Treatise on Febrile Diseases), Taiyang disease, Syndrome, Chinese medical formula, Compatibility (TCD), Hierarchical clustering analysis