Since the basic pathogenesis of relative predominance of yin and yang is the exuberance of pathogenic factors, the treatment must follow the therapeutic principle that "excess should be reduced". To be specific, excess-heat syndrome due to the exuberance of pathogenic factors of yang nature should be treated by clearing away heat while excess-cold syndrome due to the exuberance of pathogenic factors of yin nature should be treated by eliminating cold. 

Further development of relative predominance of yin and yang may lead to consumption of yin-fluid by yang-heat or impairment of yang-qi by yin-cold, which should be treated by elimination of pathogenic factors in combination with deficiency-supplementing therapy, i.e. combination of the therapy for clearing away heat with the therapy for nourishing yin or combination of the therapy for eliminating cold with the therapy for tonifying yang.

     

Since the basic pathogenesis of relative decline of yin and yang is insufficiency of the healthy qi, the treatment must follow the principle that "deficiency should be supplemented". To be specific, deficiency-cold syndrome due to insufficiency of yang-qi should be treated by nourishing yang while deficiency-heat syndrome due to deficiency of yin-fluid should be treated by nourishing yin. 

Further development of relative decline of yin and yang may lead to deficiency of yin due to prolonged deficiency of yang or deficiency of yang due to protracted deficiency of yin, bringing on deficiency of both yin and yang which should be treated by nourishing both yin and yang or mainly nourishing yang with the consideration of yin or mainly nourishing yin with the consideration of yang.

     

TCM believes that all drugs possess four properties, five flavors and four acting tendencies (namely ascending, descending, sinking and floating) which are generalized according to the theory of yin and yang. The four properties refer to cold, hot, warm and cool nature of drugs. Drugs of hot and warm nature pertain to yang while drugs of cold and cool nature belong to yin. The former are usually used to treat cold syndrome while the latter to treat heat syndrome.

      

The five flavors refer to acrid, sweet, sour, bitter and salty tastes of drugs. There is another flavor known as bland which is not as distinct as any of the five flavors. Drugs of different flavors bear different effects and are categorized differently in terms of yin and yang. For example, acrid flavor disperses, sweet flavor nourishes and bland flavor oozes. So the acrid, sweet and bland flavors pertain to yang. Sour flavor astringes, bitter flavor purges and salty flavor moistens. So the sour, bitter and salty flavors pertain to yin.

The concept of ascending, descending, sinking and floating is a generalization of the acting tendencies of drugs. Drugs tending to ascend and disperse pertain to yang while drugs tending to descend and tranquilize pertain to yin. To generalize the properties and acting tendencies of drugs with the theory of yin and yang is to guide clinic differentiation of syndrome. 

Clinically only when relative predominance or decline of yin and yang is clearly differentiated, correct therapeutic principles are decided and proper drugs are selected according to their properties, flavors and effects can satisfactory curative effect be obtained and therapeutic aim be realized.