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The six qi (liuqi) refers to an ancient Chinese concept still relied upon in today’s discussions of traditional Chinese medical practices.  The concept behind the term is that external (environmental) conditions can influence the functions of the body.  When the environmental conditions are moderate and normal (e.g., “seasonable weather”) and the person is dressed properly and protected from over exposure, the sixqi have a positive influence.  However, when the conditions become extreme, when they change rapidly, or when they do not follow the usual pattern, they are able to adversely affect health, and cause disease.  In such cases, the six qi are known as liuyin (six excesses) or even liuxie (six evils).

The term “qi” used in the description of the environmental conditions is the same as that used throughout the discussions of Chinese medicine, and refers, in this application, to the characteristics of the atmosphere and its influence on the body.  The external qi can cause the internal qi to shift.  On the positive side, this means that the six qi can nurture the body, carrying the heavenly cycle into the interior and assisting human development and expression, harmonizing the inner qi with nature.  On the negative side, weather that is extreme or unseasonal can cause internal disruption and harm, pushing the qi out of balance.  This is especially the case if the body is not fully nourished and the vessels are not rich in qi and blood: then there is insufficient protection from the potential adverse impact of the outside.  It is commonly said that if disease enters the body, it is because the weiqi (protective qi) is deficient; the situation is also expressed as the vessels being “empty” and thus readily receiving the evil from the exterior. 

While the Chinese pictogram for qi describes the fragrant, moist, warm steam in a pot of cooking rice (see Qi: Drawing a concept), the more general meaning of qi is an influence, which is the translation term used by Paul Unschuld in his books on Chinese medical history.  Hence, when the weather is moist and very warm (as occurs on a hot, humid summer day), that is something like the qi of the cooking pot; but one can also have a cold influence or a dry influence, and each of these is a type of qi.

There is some difference in concepts between the modern ideas of weather or climate and the Chinese ideas of external qi, though there is considerable overlap.  In recognition of the similarities that exist, the concept of six qi is often translated as the “six climatic influences.”  The primary difference in the traditional versus modern thinking has to do with the extent of influence of climate on the internal environment; both agree that extremes can do harm, but the Chinese view is that the atmosphere can have more health effects.

“Normal” weather in most places that humans live might cause one to feel chilly or warm, and it might cause one to feel other discomforts (e.g., flare up of arthralgia with moderately cold-damp weather), but, even when it is somewhat severe or unseasonable, it is not seen as a primary cause of diseases.  That is, the weather has some ability to affect us, but we can easily overcome that, especially as we have accomplished in recent years through a combination of carefully-crafted protective clothing, well-built houses and cars, and climate control devices (such as heaters, air-conditioners, humidifiers, dehumidifiers, air filters, etc.).  Today, vast numbers of people spend most of their time in climate-controlled environments.

By contrast, this is the situation as described in a 12th century Chinese text (1):

The six excesses are ordinary influences of heaven.  If one fails to care about their assimilation in correct proportions, they will flow into the body, starting from the major conduits and network conduits [jing and luo] and, then, unite internally in the viscera and bowels [zang and fu].  They are causes of illness that have come from the outside.

In a 16th century text, this is said (2):

Although the origins of illnesses are traceable to many causes, all of them result from something evil.  Evil is the ultimate cause of all illness.  That is to say, everything that is not part of the normal order in the human organism can cause illness, such as wind, cold, dampness, hunger, fullness, taxation, and idleness, is evil—and not solely the influences of demons and epidemic illnesses as some authors have claimed.  Just as the fish exist in water, man lives surrounded by influences [qi].  If the water is turbid, the fish waste away.  If the influences to which man is exposed are irregular, man falls ill.

Because doctors in ancient times had fewer available explanations for illness (lacking information about viruses, bacteria, genetic factors, immune system disorders), the external qi were seen as being major and direct disease-causing factors.  The six excesses (liuqi) was a concept that largely replaced the previously dominant explanation of external disease causation, which was the influence of demons (see: Demons as a cause of disease).  The six excesses were not entirely replaced later by the concept of epidemic disease (diseases associated with a transmissible factor), but did become reduced in importance, at least among some doctors, as this new transmissible factor became a focus of attention, especially at the end of the 19th century.

Modern explanations of disease causation place climatic factors mainly in the realm of indirect causes: we know, for example, that certain climatic conditions contribute to multiplication of pathogenic organisms, which can then infect the body.  In that way, climate can indirectly determine whether one is at risk of experiencing diseases such as malaria, yellow fever, and a host of other tropical infections.  Also, we know that dry climates are inhospitable to certain pollen-releasing plants and for many molds that cause inhalation-allergies, so that the climate can affect whether or not one experiences allergies (which may appear to traditional practitioners as cases of wind-damp influences).  It is known that cold weather affects the mucous membranes of the sinuses and lungs and weakens immune functions, leaving one open to viral infection.  The modern view is that the disease is caused by the virus, not by the cold weather, though it is clear that the two factors work together to determine the risk of getting the disease.  Similarly, multiple sclerosis tends to occur more frequently in people living in northern climates, which are relatively cold, but it is assumed that this is because certain pathogens, dietary habits, or other factors that are found in these northern areas cause the disease: not that the coldness causes it (once affected, the heat rather than cold exacerbates this disease).  Today, doctors generally view the influence of weather on human health as something that might enhance risk of disease or might exacerbate existing disease, whereas the traditional view was that the six qi had direct influence on health, and that the six excesses caused the disease by their very nature.  They were particularly concerned about the ability of wind to penetrate the body and cause severe consequences, including stroke.

The Advanced Textbook of Traditional Chinese Medicine and Pharmacology (3) relates this traditional view:

Wind, cold, summer-heat, damp, dryness, and fire are the six climatic factors which correspond to normal seasonal changes.  Normally, they are known as the “six qi.”  The growth of all living things depends on the existence of the six qi.  They should not be harmful, rather, they should be helpful to human beings....Human beings have learned the laws of nature through the changing features of the seasons and have adapted themselves to these changes.  Thus, the six qi normally will not cause diseases.  However, if and when the six qi become abnormal or excessive, as happens in abrupt changes in environmental conditions, and if the body’s resistance is too weak to adapt to these variations, the six qi may become the six excesses: pathogenic factors that cause diseases.  Because the six excesses are abnormal qi, they are known as the six unhealthy qi, or the six exogenous pathogenic factors.

The reference to “the body’s resistance is too weak to adapt” concerns the idea of having the vessels full of qi and blood, as well as having the internal organs in a strong rather than compromised condition.

The Oriental view is that the extremes in the environment that don’t cause drastic immediate results (as death or frostbite) are very likely to eventually cause illness.  One can even suffer from the impact of normal (non-excessive) weather patterns if one does not act harmoniously with them.  In the Neijing Suwen, the situation is described in detail (4).  For each season, the correct behaviors to harmonize with the seasonal influence [qi] are detailed, and the consequences of acting contrary are stated (see: Promoting Health During the Four Seasons for additional suggestions):

Spring: He who acts contrary to these influences shall harm his liver; cold will form within him in summer, and little remains with him for the subsequent period of growth [next spring].

Summer: He who acts contrary to these influences shall damage his heart.  In autumn he shall suffer from intermittent fevers, and little remains with him for the subsequent period of gathering.  Severe illnesses will then occur at the winter solstice. 

Autumn: He who acts contrary to these influences shall harm his lung.  Nourishment shall flow away from him in winter, and little will remain with him for the subsequent period of storing.

Winter: He who acts contrary to these influences shall harm his kidneys and suffer from paralysis and cold limbs due to rising yang influences in the spring.  Little will remain with him for the subsequent period of the creation of all things.

Thus, the ancient view is that one must live in harmony with the season (specifically, its climatic quality) to avoid illnesses that will often appear later and which will leave one especially susceptible to weather-induced patterns of the next season.  The abnormal weather patterns include “unseasonal” conditions, such as cold days in summer, and storms: these are also thought to cause disease to arise.


In China, the historical and generally accepted description of the seasons is similar to that in the West, in that there are four seasons falling into the same basic time periods.  The discordance between having four seasons and five elements has led some to depict a five season pattern, or to apply a transitional pattern for each seasonal change (thus, with the earth element conditions prevailing at the seasonal transitions), but this is not something that has filtered throughout the Chinese culture.  Cheng Wuji, in the Zhujie Shang Han Lun (1144 A.D.) wrote (2):

The Comprehensive Treatise on Yin and Yang [Yin Yang Ying Xiang Da Lun] states: the influences of spring are warm and pleasant; the influences of summer are hot and fiery; the influences of autumn are clear and cool; the influences of winter are bitingly cold.  This, then, is the order of the regular influences associated with the four seasons.

The characteristics of the seasons in China vary with the geography; China is a huge country.  It has semi-tropical parts (e.g., Guangzhou, Hong Kong, Hainan Island, Taiwan), and deserts (vast areas in the northwest); it has high mountains (e.g., from Sichuan to Tibet), and northern coastal areas (e.g., Shandong).  In each of these regions, the seasonal situations are considerably different.  Further, it was believed that the various influences could penetrate the body to differing extents. Xu Dachun (5) outlined the situation (note: the term influence is again used to translate qi throughout):

Man’s life depends on the influences of heaven and earth.  Hence, the condition of his own influences and his body differ according to the geographic region where he resides.  In the Northwest, the influences of heaven and earth enter the human body deeply, and they do so in rich quantities.  When people in the Northwest are affected by wind-cold, it is difficult to drive the evil influences out again, and heavy preparations of dredging herbs are indicated.  In the Southeast, the influences of heaven and earth remain at the body’s surface, and they do so only in small quantities.  When these people are affected by wind-cold, it is easy to drain the evil influences, and light preparations of dredging drugs are indicated.   Also, the Northwest is a cold region, and one should employ drugs with warm or hot nature.  However, sometimes people are affected by accumulations of evil influences in the center of their body, and contrary to their normal condition, they become very hot internally.  In such cases, one should use herbs with an acrid taste and a cold nature.  The Southeast is a warm region, and one should employ cooling substances for treatment.  However, it sometimes happens that both proper influences and evil influences disperse together, and, in such situations, one may easily lose one’s yang influences.  In this case, then, it is advisable to use herbs with an acrid taste and with a warm nature.  In the regions of Vietnam and Guangdong, sweat flows without end, and one is especially at risk of losing one’s yang influences.  Here, aconite and cinnamon are often used substances.  Also, the low-lying and damp territories of the central districts, or the dry territories in the high altitudes of Shanxi, these all require regimens in accordance with the specific conditions of these geographic regions.  Hence, one must ask about climate, and customs, and closely adjust to them, as soon as one enters such territories.  Differences exist not only between each prefecture; varying winds and influences exist even within one county.

As one can see from this discourse, not only the weather but also the various effects of weather on the body must be evaluated before selecting a remedy.  Thus, in the case where there is profuse sweating in oppressive hot conditions as found in the far south, cinnamon and aconite, two warming herbs, are used to recover the yang that is depleted through the continuous perspiration.

Elaborating the Six Qi

The six qi have been depicted in a number of ways.  In modern times, the six qi and the six adverse influences are presented as essentially the same thing, though the list of six categories may vary between them.  The six qi are usually depicted as wind, cold, heat, moisture, dryness, and fire.  Note that heat (shu or re) and fire (huo) represent two differing manifestations, though this distinction becomes difficult to maintain.  In recent texts on Chinese medicine, it has been said that the term heat represents an external influence, but the term fire should refer to an internal process. 

The six yin, or excesses, are: wind, cold, heat, moisture, dryness, and summer heat.  Here also there are two designations of hot conditions.  In the definitions of summer heat, there are two components: one corresponds to the original concept of “fire” as an external factor (scorching heat), so that the six qi and six yin are exactly overlapping, but the other is a particular combination of dampness and heat, and that is the dominant description relied upon today (see below: summer heat).  Basically, the six qi refer to normal weather patterns, the six excesses refer to abnormalities that can cause disease.

The group of environmental conditions comprised of hot/cold and wet/dry are pairs of opposites so easily observed that they are included as a standard part of all traditional medical systems.  They represent both external conditions and internal conditions.  Wind is a climatic condition that is observed everywhere, but given a heightened importance in the Chinese system.  Summer heat is a relatively unique description in the Chinese system, one that appears to have been a later addition to the other five that were systematically corresponding to the five elements system (wood/wind, earth/wetness, water/cold, fire/heat, metal/dryness).  Various combinations of these conditions may arise, and commonly do, so that one could have, for example, heat, moisture, and wind at the same time.

It is beyond the scope of this article to explore each of the six qi, their combinations, and the development of diseases from external causes as described in Chinese medicine; these concepts are depicted in numerous texts.  However, three of the qi will be considered here in some greater depth: cold qi because of the importance attached to it by the Shang Han Lun, and the two qi that are somewhat unique to Chinese traditional medicine: summer heat and wind.


Coldness makes things more viscous, so cold was deemed a major cause of sluggish circulation and blocked circulation.  Circulatory inhibition could cause pain, so one of the key characteristics of environmental cold influence (other than the most obvious: feeling chilled) is pain.  With sufficient exposure to cold, the circulation is so badly damaged that tissues can be destroyed, as occurs with frostbite.  Some diseases that affect circulation, such as Raynaud’s Syndrome, show a significant flare-up of symptoms with exposure to environment cold.  

Concern about the impact of cold was elevated to the highest position in Chinese medicine during the Song Dynasty with the revival of Zhang Zhongjing’s Shang Han Lun, a treatise about a severe disease or group of diseases related to coldness.  The term han in the title means cold, and shanghan, a particular type of cold related disease, was first described in the Nei Jing (ca. 100 A.D.) and then in the famous book of Zhang Zhongjing.  In his commentary on the Shang Han Lun, Chen Wuji comments (1):

If one is affected by the influences of winter, that is called harm caused by cold.  All harm received from any of the influences of the four seasons may result in an illness, but the harm caused by cold is considered to be the greatest poison because influences are involved here that cause more deaths and destruction than all the others.

He goes on to explain that many illnesses that arise in Spring and Summer were due to the adverse influence of cold during Winter.  For many centuries after the Shang Han Lun was written, and continuing up to the present, the significance of this book and its implication for medical practice has been debated.  For example, concern developed about excessive use of warming herbs that resulted from some interpretations of the Shang Han Lun, and also about the use of the book’s theories and formulas to address what was eventually deemed a new or different kind of ailment: wenbing, or feverish disease.

Avoiding coldness has long been an important lesson in Chinese medicine.  Many students of Chinese medicine are alerted to this during the first days of classes, when instructors point out that common modern dietary practices, such as drinking iced beverages, eating raw foods (especially raw, refrigerated foods, as with salads and fruits), or consuming frozen foods (e.g., ice cream) are deemed extremely debilitating under the framework of traditional Chinese medicine.  Such practices are thought to cool the stomach and spleen, reducing their ability to digest food, and, ultimately (with repeated experience) to cool the kidney, lowering the ability of the body to generate warmth, reproductive energy, and even brain power.  In like manner, there is much concern expressed over failure to dress warmly for winter (especially, failing to protect the lower back and abdomen), turning to light clothing too early in the Spring, sitting in chilly air-conditioned rooms, and consuming cold-natured herbs. 

All this concern, whether justified or not, reflects both the historical importance of cold as a pathological feature in the field of Chinese medicine and also the particular situation in China.  Although the Chinese had no refrigeration or air-conditioning, they learned early on that raw foods could cause extreme problems.  This was not so much because of their rawness, as we know now, but actually because uncooked foods were usually contaminated with bacteria or worms that could have devastating and lasting effects on the digestive system as well as on the whole body.  Similarly, non-boiled water was a serious problem, and it was not yet established that if water is boiled and saved in a clean, sealed container, it will remain safe to drink even if cool or cold.  Instead, it was known that boiled water was safer than cold water.  While it is true that consuming lots of cold drinks will chill the stomach and reduce the circulation in the stomach lining that influences digestion, the problem with iced drinks in modern times is not nearly so severe as the problem of non-boiled water was in China, so it is sometimes given exaggerated importance. 


The Chinese concern about wind arises from ancient times.  It appears that early beliefs were that the world was populated with vast numbers of benevolent spirits and malevolent ghosts that influenced the course of human events (and could be influenced by shamans of skill).  If a person became ill, especially if the onset was sudden, the cause might be attributed to entry into the body of an evil spirit.  As an example, if someone suffered a heart attack or stroke, or suddenly had a severe pain, loss of consciousness, loss of motor abilities, or died, it was thought that such a spirit had gotten in and caused it at that time.  Since some of the demons were said to travel with the wind, such a disease was called “being struck by wind;” such terminology became especially prominent after demon-causation was devalued as the principle description of the problem.  It did not necessarily mean that the person was standing outdoors in windy weather and the blowing wind itself caused the disease, though, this explanation had been applied in the past, and continues to be relied upon today.  In the modern book English-Chinese Encyclopedia of Practical Traditional Chinese Medicine (6) it is said that “Wind, prevailing in the Spring, exists all the year round.  Wind in excess, called wind pathogen, can cause disease.”

As the medical descriptions moved away from demon-caused disease to nature-caused disease, wind became the first and most important of the external causes. The concept soon evolved into the six qi and six yin.  Though wind became specifically affiliated with the Spring season, this season is not necessarily the one in which there is more wind, as we conceive of wind today.  In the English-Chinese Encyclopedia, it is explained: “Wind-pathogen is the predisposing factor contributing to exopathic [externally caused] diseases while all the other pathogenic factors, such as cold-pathogen, damp-pathogen, dry pathogen, usually invade the human body in association with wind pathogen.”  This way of looking at wind focuses on the idea of invasion of a pathogenic influence, more so than simple influence of the external conditions on the body.

Wind-dispelling herbs, and some acupuncture treatments, were said to open up the pores through which the demons or, in later times, the invading wind-pathogen, could be let out.  In this sense, many of the herbal therapies for wind disorders were used to induce diaphoresis (see: Eight methods of therapy), whether the treatment was for stroke, heart attack, common cold, sore throat, skin eruption, or any other disorder that arose suddenly.

The importance of treating wind disease is described by Xiu Dachun (5):

Whenever someone has been incidentally affected by wind-cold resulting in headache, fever, cough, and running nose, this is called, in everyday language, harm caused by wind....The fact is that the illness of harm caused by wind starts from the skin and its hair to enter the lung....All these conditions are considered minor illnesses, and the people affected by such problems neither avoid wind and cold, nor do they care about what they eat and drink.  Over the years, and with every month, the workings of the illness penetrate the body deeper and deeper every day.  In some cases, pathoconditions appear indicating the blood has been affected.  Or the lung may cease to function properly, or panting may develop, or disquietude coupled with weakness.  It is always the same, and the damage caused by erroneous treatments cannot be measured.  As the proverb goes: “If one does not pay attention to harm caused by wind, the illness will change to fatigue.”  Well said!  But how to conduct a treatment?  First, the wind is to be expelled with herbs like perilla leaf and schizonepeta; second, phlegm is to be dissolved with herbs like pinellia and fritillaria; third the influences are to be brought down with herbs like perilla seed and peucedanum; fourth; the constructive and protective influences are to be harmonized with herbs like cinnamon twig and peony; fifth, the body’s fluids are to be enriched with herbs like trichosanthes seed and scrophularia; sixth, the blood is to be nourished with herbs like tang-kuei and gelatin; seventh, the fire is to be cooled with herbs like scute and gardenia; and eighth, the lungs are to be regulated with herbs like morus bark and arctium.


The description of the six qi and six excesses, includes heat qi.  Why did the Chinese add summer heat to the list of excesses?  According to the Advanced Textbook..., “heat is an exogenous pathogenic factor that can be classified into various types, such as wind-heat, summer-heat, and damp-heat.”  This suggests that heat is a factor that tends to alter others, such as wind and dampness.  The reason for including summer heat as a separate entity is that there were certain diseases that stood out during summer that differed from heat disorders occurring at other times of year.  The Advanced Textbook... says: “Diseases caused by summer-heat are only seen in this season....Summer heat is an exogenous pathogenic factor; there is no endogenous summer heat at all.”  The other qi each have a corresponding internal cause (e.g., cold qi can occur internally from fear or from weakening of the yang of the kidney; wind qi can occur internally from anger or from deficiency of the liver blood and yin, etc.). 

Summer-heat disease can include symptoms of excess yang (high fever, fidgets, flushed face) and consumption of body fluid due to the heat (thirst, scanty urine), which corresponds to attack by “fire,” but the characteristic of summer-heat disease is the dampness syndrome.  The description that arises is a pattern of fever, fidgets, thirst, weakness of the limbs (this occurs because of depletion of body fluids), tightness in the chest, nausea, loose stools, and sluggishness.  Such conditions may be more common in wet summer situations in which the food and water become contaminated with micro-organisms (see Pill Curing and Huoxiang Zhengqi San).  These pathogens taken in with food produce a symptom complex that may appear different than anything generated by internal processes or usual external influences, and occurs most often in the semi-tropical summers of southern China where it is rainy during that season.  Summer heat could be a serious disease.  Here is what Xu Dachun observed (5):

I have seen people who had been hit by summerheat and who drank a bowl of strong ginger tea.  They died as fast as it took them to turn their cup.  If one takes a perilla leaf decoction, any cold will be dispersed immediately, and if the illness was caused by summer heat or ordinary heat, the intake of perilla leaf would not cause any damage either.  The reason is that perilla leaf has a dispersing nature; it always disperses, regardless of the pathocondition present.

Perilla leaf, known to the Japanese as shiso (the Chinese is zisu, or zisuye), is taken with raw fish to kill parasites that may be ingested with them.  Today, Chinese physicians often rely on huoxiang (agastache or pogostemon) for the summer heat syndromes, along with or in place of perilla leaf. 

  1. Unschuld PU, Introductory Readings in Classical Chinese Medicine, 1988, Kluwer Academic Publishers, Holland.
  2. Unschuld PU, Medicine in China: A History of Ideas, 1985 University of California Press, Berkeley, CA.
  3. State Administration of Traditional Chinese Medicine, Advanced Textbook on Traditional Chinese Medicine and Pharmacology, (4 vol.) 1995–6 New World Press, Beijing.
  4. Veith I, The Yellow Emperor’s Classic of Internal Medicine, 1966 University of California Press, Berkeley, CA.
  5. Unschuld PU, Forgotten Traditions of Ancient Chinese Medicine, 1990 Paradigm Publications, Brookline, MA.
  6. Xu Xiangcai (chief ed.), The English-Chinese Encyclopedia of Practical Traditional Chinese Medicine, (21 vols.) 1989 Higher Education Press, Beijing.


November 2010