The basic concepts of the Six Qi, Six Evils, and Five Pathogenic Factors: 1. Six Qi and Six Evils (1) Six Qi: The so-called Six Qi, also known as the Six Origins, refers to the six normal climatic conditions of wind (feng), cold (han), heat (shu), dampness (shi), dryness (zao), and fire (huo). The changes in Six Qi are referred to as the Six Transformations. These normal climatic changes are conditions for the growth of all things and are harmless to the human body. Due to the body’s self-regulatory mechanisms during life activities, it develops a certain adaptability, allowing physiological activities to align with the changes in Six Qi. Therefore, normal Six Qi generally does not easily cause illness. (2) Six Evils: The so-called Six Evils refers to the collective term for the six external pathogenic factors of wind, cold, heat, dampness, dryness, and fire. The shifts in yin and yang, the alternation of cold and heat, and climatic changes all follow certain rules and limits. If climatic changes are abnormal, such as excessive or insufficient Six Qi, or if the Qi appears at the wrong time (for example, cold in spring when it should be warm, or heat in winter when it should be cool), or if climatic changes occur too abruptly (such as sudden cold or warmth), exceeding certain limits, the body may not be able to adapt, leading to the onset of disease. Thus, Six Qi transforms from being harmless to harmful, becoming a pathogenic factor. The Six Qi that can lead to disease is termed “Six Evils.” While there is a close relationship between climatic changes and the onset of disease, not everyone will become ill due to abnormal climatic changes. Some individuals can adapt to these changes without falling ill, while others cannot and do become sick. For the former, the same abnormal climatic change is considered a Six Evil. Conversely, even in normal climatic conditions, such as favorable weather, some individuals may still fall ill due to low adaptability. This normal change in Six Qi can also be a “Six Evil” for those with pre-existing conditions. Thus, it is evident that Six Evils exist objectively in both abnormal and normal climatic conditions. The decisive factors here are the differences in individual constitution and the strength of Zheng Qi (正气, vital energy). Only when the body’s Zheng Qi is insufficient and resistance decreases can Six Qi become pathogenic and invade the body, causing illness. In this sense, Six Evils are a category of pathogenic factors that disrupt the relative dynamic balance of the body due to changes in Six Qi, leading to external pathogenic diseases. “Six Evils” is also known as “Six Xie” (六邪). 2. External Six Evils and Internal Five Pathogenic Factors: External Six Evils are pathogenic factors of external origin, referred to as external Xie, while Internal Five Pathogenic Factors refer to the pathological changes caused by the imbalance of yin, yang, Qi, and blood in the organs, including internal wind, internal cold, internal dampness, internal dryness, and internal heat (fire), which belong to the realm of pathophysiology.
The clinical manifestations of Internal Five Pathogenic Factors, while similar to the pathogenic characteristics and pathological responses of the Six Evils (wind, cold, dampness, dryness, fire), are distinguished from the external wind, external cold, external dampness, external dryness, and external heat (fire) by the prefix “internal,” hence termed “Internal Five Pathogenic Factors.”
The clinical manifestations of Internal Five Pathogenic Factors generally do not present with exterior symptoms, often manifesting as either deficiency or excess, or a mixture of both. When External Six Evils act on the body, they cause dysfunction in the yin, yang, Qi, and blood of the organs, leading to pathological changes that often present with exterior symptoms and are mostly excess conditions. Pure summer heat does not typically present with exterior symptoms, but when combined with dampness, it is termed summer dampness, which does present with exterior symptoms. Only when an external evil directly invades does it lead to interior symptoms. External Six Evils and Internal Five Pathogenic Factors, while distinct as pathogenic factors and pathological results, are closely related. When Six Evils harm the body, they affect the interior, damaging the organs, which can easily lead to the harm of Internal Five Pathogenic Factors. Conversely, when Internal Five Pathogenic Factors cause dysfunction in the organs, they can also easily be affected by the Six Evils.