1. The Six Evils

1. The Six Evils

These are wind, cold, summer heat, dampness, dryness, and fire. They are originally six types of climate change in nature, normally referred to as the "Six Energies." When these six natural phenomena exceed the range that the human body can adapt to—sometimes too much, sometimes too little—they become pathogenic factors. Here, the "Six Evils" specifically refer to situations where the Six Energies are either too much or too little. "Evil" means "pathogenic," referring to conditions that are either excessive or insufficient.

(1) Wind

"Wind is the chief of all diseases," meaning wind can combine with any pathogenic factor to cause illness, such as wind-cold, wind-damp, wind-heat... "Wind moves quickly and changes constantly," meaning wind is fast-moving and unpredictable, such as when extreme heat generates wind or when liver wind stirs internally, both of which develop very rapidly; there are also cases of wind-damp migrating and pain having no fixed location. Wind belongs to the wood element, is flexible and promotes dispersion, so treatments for wind-pathogens mostly focus on dispersing them.

(2) Cold

Cold has a contracting effect; contraction leads to blockage, and blockage leads to pain. Therefore, most pain syndromes are effectively treated by warming and dispersing. Cold easily harms yang, and wherever cold exists, yang energy will inevitably be deficient. Thus, almost all herbs used to dispel cold have yang-tonifying properties.

(3) Summer Heat

Summer heat is hot and depletes qi and injures fluids. This means summer heat has both a fiery nature that can injure yin and a tendency to deplete qi. Summer heat is often accompanied by dampness, meaning summer illnesses often involve vomiting and diarrhea. Additionally, summer illnesses occur in the unique environment of summer, hence the term "summer heat."

(4) Dampness

Dampness is heavy and tends to descend, with the lower jiao often showing signs of dampness in clinical practice. Dampness is sticky and difficult to remove quickly, so any condition accompanied by dampness tends to have a long course, such as wind-cold or wind-heat, which may heal in a few days, while wind-damp may drag on for a long time. Similarly, ascites, pleural effusion, and joint effusion are all examples of dampness-related conditions, characterized by a long course. Dampness is heavy and easily obstructs the flow of qi; when qi flow is blocked, pain occurs, so most pain-relieving medicines have a dampness-dispersing effect.

(5) Dryness

Dryness is prevalent in autumn, hence the term "autumn dryness." Dryness manifests as dry eyes, dry nose, and dry mouth. Dryness is a yang-pathogen that easily injures body fluids.

(6) Fire

Fire's upward-flaming nature is an important concept in TCM for treating fire-related conditions. When fire arises in the lower jiao, it often combines with dampness to cause illness; otherwise, it cannot cause illness. Hence the saying, "There is no pure fire in the lower jiao." Fire easily injures yin, so any formula that clears fire should be paired with yin-nourishing herbs to enhance its effectiveness, such as Zhimu in Baihu Tang, Shengdi in Longdan Xiegan Tang, and Diguopi in Xiebai San. Fire also easily causes uncontrolled bleeding, with more than half of bleeding cases caused by fire, so clearing fire can stop bleeding. The representative formula for this is Sanhuang Xie Xin Tang.