In Traditional Chinese Medicine (TCM) theory, regardless of how many pathogenic factors exist, there are only five major categories of disease causes. Mastering these five categories allows one to address all pathogenic factors.
Content of this issue:
1.Six Excesses
2.External Wind
3.Internal Wind
4.Treatment of Internal and External Wind
1.Six Excesses
The Six Excesses, or Liù Yín (六淫), refer to the six types of external pathogenic factors: Wind, Cold, Heat, Dampness, Dryness, and Fire.
Wind, Cold, Heat, Dampness, Dryness, and Fire are six different climatic conditions in nature, referred to as the “Six Qi.” When the climate in nature becomes abnormal, exceeding the body’s ability to adapt, or when the body’s righteous Qi is insufficient to resist the destructive effects of the Six Qi on the body’s balance, these Six Qi become pathogenic factors, known as the Six Excesses.
Humans live in the environment created by heaven and earth, constantly surrounded by the climate formed by them. The Six Qi are the most common physical pathogenic factors affecting human function, thus TCM initially used this to represent the five categories of external pathogenic factors (Heat and Fire belong to the same category). These five categories summarize all pathogenic factors from the outside that affect human function, whether they are physical, chemical, or biological factors, as long as they cause similar changes in the patient’s body, they can be considered the same type of pathogenic factor.
2.External Wind
The wind in nature is characterized by movement; leaves fluttering and waves on the water surface indicate that the wind has risen. The essence of natural wind is flowing gas.
Wind is a Yang pathogenic factor, belonging to Wood, and is active. The effect of Wind on the human body can scatter Yang Qi and move Yin fluids. Any factor that can achieve the effect of “scattering Yang Qi and moving Yin fluids” after acting on the human body can be classified as Wind.
Wind enters from the outside, dispersing the defensive Qi, causing the Yang to be insufficiently dense, stirring the Yin fluids, leading to symptoms such as sweating and aversion to wind; stirring the Qi and blood upwards, resulting in symptoms like nasal congestion and dry retching; stirring the Qi and blood outward, causing symptoms like fever.
Many foundational TCM theory books explain “Wind is characterized by its ability to act and change frequently” as a feature of Wind pathogenicity, believing this phrase refers to the migratory nature of diseases caused by Wind, and thus consider “wandering joint pain, pain without a fixed location” as diseases primarily caused by Wind. However, Zou Shizhen believes this interpretation is incorrect. “Wind is characterized by its ability to act and change frequently” precisely describes the hyperactive nature of Wind; “wandering joint pain, pain without a fixed location” is not primarily due to excessive Wind, but rather indicates that the condition is still mild, and the Qi and blood have not completely stagnated in one area, with the pathogenic factors still being Wind, Cold, and Dampness.
Wind is present in all seasons, infiltrating everywhere, making it a significant external pathogenic factor, often combining with other pathogens to harm the body, referred to as the “Leader of All Diseases.” Cold, Dampness, Heat, Dryness, and other evils often attach to Wind and invade the human body, leading to external Wind-Cold, Wind-Dampness, Wind-Heat, and Wind-Dryness syndromes. These syndromes are generally dominated by Cold, Dampness, Heat, or Dryness, with Wind merely acting as a carrier.
3.Internal Wind
Heaven and Earth form a large dynamic balance system, containing the Six Qi of Wind, Cold, Heat, Dampness, Dryness, and Fire. Humans live within this system and are affected by these Six Qi, which are essentially the Five Elements of the larger system acting upon the Five Elements of the human body. The human body itself is also a dynamic balance system, possessing its own Five Elements, thus it can also generate its own Wind, Cold, Heat, Dampness, Dryness, and Fire. The former is referred to as external Six Excesses, while the latter is generally called internal Five Evils (ancient texts rarely mention Heat in the context of internal evils). Although both share the same name, their essence is entirely different.
Many TCM theoretical texts do not strictly differentiate between the two, leading to conceptual confusion. Zou Shizhen believes: external Six Excesses as diseases are caused by the Six Excesses in nature affecting the body’s function, while internal Five Evils arise when certain pathogenic factors disturb the body’s balance, causing phenomena similar to the Six Qi in nature. Therefore, internal Five Evils are not, in essence, pathogenic factors, but rather manifestations of disease. The reason for discussing internal Five Evils alongside external Six Excesses in the study of etiology is primarily to help readers recognize the distinctions between concepts that are often expressed using the same terminology in ancient TCM texts. In these texts, the frequency of Wind’s appearance is very high; sometimes it refers to external Six Excesses’ Wind, and sometimes it refers to the internally generated Wind, with completely different connotations but without clarification, leading to many misunderstandings in later studies.
The wind in nature is characterized by movement: leaves shaking, water surface rippling, indicating the presence of wind. Therefore, abnormal movements in the human body, such as spasms of the limbs, arching of the back, head shaking, muscle tremors, dizziness, etc., are also referred to as Wind in TCM, which is Internal Wind.
Movement is merely a characteristic phenomenon of Wind; the essence of natural wind is rapid air flow, while the essence of Internal Wind is abnormal flow of Qi and blood within the body. As long as there is rapid air flow, wind will occur in nature. Thus, there are many causes for the generation of wind in nature: it can be due to temperature differences, a fan blowing, or a sudden narrowing of a passageway in the air, creating a wind tunnel.
Similarly, any factor that can cause abnormal flow of Qi and blood can lead to the generation of Internal Wind. The causes of abnormal flow of Qi and blood in the body are not limited to one: extreme heat can generate Wind, extreme cold can also generate Wind; Blood deficiency can generate Wind, Blood stasis can also generate Wind; Phlegm obstructing the meridians can create a wind tunnel in the pathways of Qi and blood, leading to Internal Wind.
4.Treatment of Internal and External Wind
Although most TCM texts directly refer to diseases related to Internal Wind simply as Wind, most of these diseases have little relation to external Wind pathogenic factors. One cannot assume that just because the name contains Wind, it has a necessary connection to External Wind.
Treating diseases caused by External Wind primarily involves expelling External Wind, while treating these diseases requires identifying the causes of abnormal Qi and blood flow for targeted treatment, such as nourishing Blood for Blood deficiency generating Wind, clearing Heat for extreme Heat generating Wind, and resolving Phlegm obstructing the meridians for Phlegm-induced Internal Wind, etc.
One should not assume that upon hearing the term Wind in a disease name, it necessarily requires expelling Wind; medications for expelling External Wind are often pungent and warm, which can easily deplete Blood and injure Yin. If used to treat patients with Blood deficiency generating Wind, it will not only be ineffective but may also worsen the condition. Whole scorpion and centipede are common Wind-extinguishing herbs; many TCM practitioners tend to use these herbs for patients with Internal Wind, which is also incorrect. These herbs can extinguish Wind because they can resolve Phlegm obstructing the meridians, but both are pungent and warm substances, and if used for extreme Heat generating Wind, they will not only be ineffective but may also exacerbate the condition.