Disharmony of Yin and Yang

Disharmony of yin and yang refers to pathological changes involving either excess or deficiency of yin or yang, occurring when the body is invaded by pathogenic qi. Disease will not occur unless the body is invaded by pathogenic factors which cause derangement of yin and yang in the interior. Yin - yang disharmony, i.e. excess or deficiency of either yin or yang, is mainly manifested in the form of cold and heat, and excess and deficiency syndromes. In general, heat syndromes of excess type will occur in cases of excess of yang, and cold syndromes of excess type in cases of excess of yin. Cold syndromes of deficiency type will occur in cases of deficiency of yang, and heat syndromes of deficiency type in cases of deficiency of yin. In addition, in the course of the progression of disease, cold syndromes may manifest some false heat symptoms, in which excess of yin walls off yang, and heat syndromes some false cold symptoms in which excess of yang walls off yin.

All the contradictions and changes occurring in the disease process can be generalized in terms of yin and yang. Thus all the zang - fu organs and meridians are classified in terms of yin and yang ; and qi and blood, nutrient qi and defensive qi, exterior and interior, ascending and descending of qi reflect yin and yang contradictions. Functional disturbance, derangement between qi and blood and between nutrient and defensive qi all belong to disharmony of yin and yang, which underlies the whole disease process and is the decisive factor in the occurrence and development of disease.