Anti-pathogens eliminate pathogens, and pathogens consume anti-pathogens. If the anti-pathogens triumph, the disease improves or disappears; if the pathogens triumph, the disease progresses.
(1)Disharmony between Yin and Yang produces disease. Yin–Yang imbalance attracts disease, or is a disease property generally. Normally, Yin and Yang maintain balance with interdependence, inter-consumption, and inter-transformation. Yin–Yang balance is damaged by external pathogens, emotional factors, improper nutritional intake, overwork, excessive leisure, etc. Yin–Yang disharmony may lead to disharmony among the Zang-Fu, meridians, Qi, blood, body fluid, etc. Different, complicated pathogenic changes may appear. Yin–Yang disharmony includes Yin-Yang decrease of either Yin or Yang, and Yin–Yang increase of either Yin or Yang.
- Yin increase causes excessive cold syndromes. Increased Yin’s bodily effect is a Yin-Qi-predominant hypofunction. It is an excessive cold syndrome with Yin predominance and Yang normality. It may be caused by Yin pathogens such as external cold–damp pathogens or too much intake of raw or cold food.
- Yin decrease causes a deficient heat syndrome. Decreased Yin’s bodily effect is the overconsumption of Yin essence, deficient congenital Yin essence, damaged Yin essence due to insufficient acquired nutrition, or disease-induced deficient Yin.
- Yang increase causes excessive heat syndromes. Increased Yang’s bodily effect is a Yang-Qi-predominant hyperfunction. It is an excessive heat syndrome with Yang predominance and yin normality. It may be caused by Yang pathogens such as external heat pathogens or heat pathogens derived from cold pathogens, or emotional pathogens.
- Yang decrease causes a deficient cold syndrome. Decreased Yang’s bodily effect is the overconsumption of Yang-Qi, deficient congenital Yang-Qi, declined Minmeng Fire, or damaged Yang-Qi due to insufficient acquired nutrition.
(2)Yin–Yang consume each other, or a deficiency of one may consume the other. Yang may be consumed by damaged Yin. Chronic Yin deficiency syndrome may gradually suffer from deficient Yang, leading to Yin deficient syndrome with Yang deficiency. Yin may be consumed by damaged Yang. Chronic Yang deficiency syndrome may gradually suffer from deficient Yin, leading to Yang deficient syndrome with Yin deficiency.
(3)Yin–Yang mutual rejection is a critical status of their disharmony.
- Yin may bc predominant in rejecting Yang, meaning that the excessive cold Yin pathogens in the inner body reject Yang, which resides in the external body. It may manifest as internal true cold and external false heat.
- Yang may predominate in rejecting Yin, meaning that the excessive heat Yang pathogens in the internal body reject Yin, which resides in the external body. It may manifest as internal true heat and external false cold.
(4)Yin–Yang transform into each other, meaning that a Yang heat syndrome may transform into a yin cold syndrome and vice versa. For example, when the Yang heat syndrome lasts for too long, the Yin cold syndrome may appear. On the other hand, when the Yin cold syndrome lasts for too long, the Yin heat syndrome may appear.
(5)Yin–Yang loss may include both Yin loss and Yang loss. This mainly means that the Yin fluid suddenly loses or that Yang-Qi suddenly loses. Both of them are in a critical status. The Yang loss may result from Yang deficiency with overwork or oversweating due to improper treatment. The Yin loss may result from excessive heat pathogen-induced massive vomiting, sweating, or diarrhea.