In Chinese medicine, illness does not simply appear out of nowhere. Something causes it. For diseases that come from outside the body, TCM identifies six environmental forces called the Liu Yin, or Six Evils: wind, cold, heat, dampness, dryness, and summerheat. These are not abstract concepts. They describe real patterns of how the body reacts to environmental stress.
Wind is considered the chief of the Six Evils because it carries other pathogens into the body. Think of how a cold wind drives rain into your bones. In TCM, wind behaves the same way. It is rapid, changeable, and moves. Symptoms that come and go suddenly, that migrate from one joint to another, or that involve twitching and spasms carry the signature of wind.
The classic example is the common cold. When you catch a chill after being exposed to wind, the first symptoms are usually in the upper body: stiff neck, headache, sneezing. Wind enters through the pores and disrupts the body’s defensive qi. Herbs like Jing Jie (Schizonepeta) and Fang Feng (Saposhnikovia) are used to expel wind from the surface.
Cold causes contraction. When cold enters the body, muscles tighten, blood vessels constrict, and pain follows. A patient with cold-pattern lower back pain will notice that the pain worsens in cold weather and improves with warmth. The tongue will be pale, the pulse tight.
TCM treats cold with warming. Herbs like Gui Zhi (Cinnamon Twig) and Ma Huang (Ephedra) in the formula Gui Zhi Tang warm the body’s surface and promote sweating to push cold out. Moxibustion, the burning of mugwort over acupuncture points, is another powerful tool against cold.
Heat causes expansion, redness, and agitation. A high fever with a red face, sore throat, and rapid pulse is a classic heat pattern. Heat dries up fluids, so the patient may also have a dry mouth, dark urine, and constipation.
Treatment involves clearing heat with herbs like Shi Gao (Gypsum) and Zhi Mu (Anemarrhena). The famous formula Bai Hu Tang (White Tiger Decoction) is used for intense heat with high fever. For heat that has penetrated deeper into the body, Qing Hao (Sweet Wormwood) and Di Gu Pi (Lycium bark) are employed.
Dampness is the most stubborn of the Six Evils. It is heavy, sluggish, and hard to dislodge. Symptoms include a feeling of heaviness in the body, sticky discharge, bloating, and a tongue with a thick greasy coating. Dampness tends to linger and recur.
Modern life breeds dampness: sitting too much, eating too much cold or sweet food, living in humid environments. Herbs like Cang Zhu (Atractylodes) and Hou Po (Magnolia Bark) dry dampness. The formula Ping Wei San is a classic prescription for dampness obstructing the Spleen and Stomach.
Dryness depletes the body’s fluids. It is most common in autumn, when the air turns crisp and the skin begins to crack. Symptoms include dry cough, dry skin, dry eyes, and constipation with dry stools. The tongue coating is thin or absent.
TCM treats dryness by nourishing fluids. Herbs like Sha Shen (Glehnia) and Mai Men Dong (Ophiopogon) moisten the lungs and throat. Sang Xing Tang is a well-known formula for wind-dryness attacking the lungs.
Summerheat only strikes during the hottest months. It combines heat with dampness, causing symptoms like fever, heavy sweating, dizziness, and nausea. The patient often looks flushed but feels simultaneously hot and sticky.
The classic remedy is Huo Xiang Zheng Qi San, a formula containing Huo Xiang (Agastache) that dispels summerheat-dampness and regulates the Spleen and Stomach. In China, this formula is a household staple during summer heatwaves.
Despite the ominous name, the Six Evils are not inherently malevolent. They are simply environmental forces that become pathological when the body’s defenses are weak. A healthy person with strong zheng qi (upright qi) can walk through wind and cold without falling ill. The evil only succeeds when the door is left open.
This understanding shifts the focus from killing pathogens to strengthening the host. It is why TCM places such emphasis on prevention, lifestyle, and building resilience. The Six Evils remind us that we are not separate from our environment. We are in constant conversation with it, and health means staying in harmony with the world around us.
Professor Zhao Hanqing is a senior TCM practitioner at Beijing Heniantang, specializing in traditional Chinese medicine theory, classical formula research, and TCM informatics. With years of clinical experience and academic dedication, Professor Zhao bridges the wisdom of ancient Chinese medical classics with modern computational approaches to advance the field of TCM knowledge systems.
Disclaimer: This article is presented for educational and informational purposes. Individual results may vary. Always consult qualified healthcare providers before beginning any treatment.
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