In Traditional Chinese Medicine (TCM), the term “Six Excesses” (六淫, liù yín) refers to the six external pathogenic factors: Wind (风, fēng), Cold (寒, hán), Heat (暑, shǔ), Dampness (湿, shī), Dryness (燥, zào), and Fire (火, huǒ). The balance of Yin and Yang, as well as seasonal changes, follows certain patterns and limits. When climatic changes are abnormal, leading to excessive or insufficient manifestations of these six Qi, or when they occur out of season, or when changes are too abrupt, the body may fail to adapt, resulting in disease. Thus, the six Qi transform from being harmless to harmful, becoming pathogenic factors.
The characteristics of diseases caused by the Six Excesses include the following aspects:
External Pathogenicity
The Six Excesses are primarily external pathogens that often invade the body’s surface or enter through the mouth and nose, hence they are also referred to as “external pathogens of the Six Excesses”. The diseases caused are collectively known as external diseases.
Seasonality
Diseases caused by the Six Excesses often exhibit clear seasonal patterns. For example, Wind diseases are more common in spring, Heat diseases in summer, Damp diseases in late summer, Dryness diseases in autumn, and Cold diseases in winter. However, multiple pathogenic factors can occur in a single season.
Geographical Variability
The occurrence of diseases caused by the Six Excesses is often closely related to the living environment. For instance, the northwest plateau region is prone to Cold and Dry diseases, while the southeast coastal areas are more susceptible to Damp and Warm diseases.
Coexistence
The Six Excesses can invade the body either individually or in combination. For example, Cold can directly invade the internal organs causing diarrhea, or multiple pathogens can simultaneously affect the body, such as Wind-Heat colds, Cold-Dampness affecting the Spleen, or Wind-Cold-Dampness causing joint pain.
Transformation
Although each of the Six Excesses has its own characteristics, they are not isolated; they can influence each other and under certain conditions, their pathological nature can transform. For instance, Cold can become Heat due to stagnation, prolonged Dampness can transform into Dryness harming Yin, and all Six Excesses can transform into Fire under heat conditions. The reasons for transformation include individual constitution differences and improper treatment.
Environmental Influence
The diseases caused by the Six Excesses are also closely related to the environment. For example, prolonged exposure to damp environments can lead to Dampness-related diseases, while those working in high temperatures often experience Dryness or Fire-related diseases.
The specific characteristics of each pathogenic factor are as follows:
1. Wind Pathogen
(1) Wind is a Yang pathogen, characterized by its ability to disperse and invade Yang positions.
“Those harmed by Wind are first affected in the upper body.”
(2) Wind is known for its rapid movement and frequent changes.
(3) Wind is proactive.
“When Wind prevails, movement occurs.”
(4) Wind is the chief of all diseases.
“Among the Six Qi, only Wind can fully combine with the other five Qi. For instance, when combined with Cold, it is called Wind-Cold; with Heat, it is Wind-Heat; with Dampness, it is Wind-Damp; with Dryness, it is Wind-Dry; and with Fire, it is Wind-Fire. This is because Wind can stir these five Qi and harm people, hence it is called the chief of all diseases. The other five Qi cannot fully combine with each other; for example, Cold cannot combine with Heat or Fire, and so on. Therefore, many diseases arise from Wind.”
2. Cold Pathogen
(1) Cold is a Yin pathogen that easily harms Yang Qi.
“When Yin prevails, Yang becomes ill.”
(2) Cold causes stagnation and is primarily associated with pain.
“When Cold enters the meridians, it causes stagnation, leading to pain; if it resides outside the pulse, it results in blood deficiency; if it resides within the pulse, it causes Qi obstruction, leading to sudden pain.”
(3) Cold causes contraction.
“Cold causes Qi to contract.”
3. Heat Pathogen
(1) Heat is a Yang pathogen characterized by its inflammatory nature.
(2) Heat tends to rise and can disturb the mind, depleting fluids and Qi.
“When it is intense, the pores open, and the Ying and Wei Qi communicate, leading to excessive sweating and Qi depletion.”
(3) Heat often carries Dampness.
4. Dampness Pathogen
(1) Dampness is a Yin pathogen that easily obstructs Qi movement and harms Yang Qi.
It easily injures Spleen Yang; “When Dampness prevails, it leads to diarrhea; if severe, it can cause water retention and swelling.”
(2) Dampness is heavy and turbid.
(3) Dampness is sticky and diffusive.
(4) Dampness tends to descend and easily invades Yin positions.
“Yang is harmed by Wind, while Yin is harmed by Dampness; those harmed by Wind are first affected in the upper body, while those harmed by Dampness are first affected in the lower body.”
5. Dryness Pathogen
(1) Dryness is characterized by its arid nature, easily harming body fluids.
“When Dryness prevails, it leads to dryness; all dryness and cracking are attributed to Dryness.”
(2) Dryness easily harms the Lungs.
6. Fire Pathogen
(1) Fire is a Yang pathogen characterized by its inflammatory nature.
(2) Fire easily disturbs the mind.
(3) Fire easily depletes fluids and Qi.
“Intense Fire consumes Qi.”
(4) Fire easily generates Wind and stirs the blood.
“Extreme Heat generates Wind.”
(5) Fire easily leads to swelling and sores.
“Abscesses and sores originate from Fire toxicity.”
In TCM, in addition to identifying the Six Excesses as causes of disease, the characteristics of the Six Qi are also linked to the symptoms of the disease, forming disease names such as Wind Syndrome (风证, fēng zhèng), Cold Syndrome (寒证, hán zhèng), Damp Syndrome (湿证, shī zhèng), Fire Syndrome (火证, huǒ zhèng), Dryness Syndrome (燥证, zào zhèng), etc. These syndromes have a certain causal relationship with the Six Excesses.
For example, Wind invasion can lead to external Wind-Cold, but some conditions may not be classified as external diseases yet exhibit similar symptoms to Wind, Cold, Dampness, or Fire, such as Wind rash, which typically presents with rapid onset, quick resolution, and itching, resembling the characteristic of Wind’s “ability to move and change frequently”. It is generally believed to be caused by Wind, but imbalances in the functions of the organs, Yin, Yang, Qi, and blood can also produce symptoms and characteristics similar to those of the external Six Excesses.
