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XING: On The Nature Of Herbs
and the Misuse of the term Temperature

essay by Subhuti Dharmananda, Ph.D., Director, Institute for Traditional Medicine, Portland, Oregon

It is somewhat surprising to me how many Western practitioners of Chinese medicine refer to the nature [xing] or qi of an herb as the herb’s temperature, which is not a suitable translation term and ought not to be used in this context.  Temperature has a very distinct meaning in the Western world, as we speak of temperature on a daily basis in terms of the weather and indoor environment, water that we enter (e.g., swimming pool or spa), in relation to cooking of food, and our body.  These are references to measurements that have a consistent application and meaning in relation to thermal energy.  Because of the wide-spread use of the term, it carries with it certain connotations based on shared experiences.  Yet, one can find descriptions of Chinese herb properties aimed at non-practitioners who have no way to know the actual meaning, such as this:

The way that an herb acts within the body—and hence its therapeutic effect—is determined by its temperature, its taste and the channels/meridians that it enters. An herb’s temperature is classified as hot, warm, neutral, cool or cold.   In line with common sense, cool and cold herbs are used to treat hot conditions, while warm and hot herbs are used to treat cold conditions.

Indeed, hot conditions and cold conditions are often not associated with changed body temperature; further, there are several instances where warming herbs are used in treating “hot” conditions, so the common sense really applies only to actual temperature issues, which are not the focus of herbal properties or diagnostic categories.  Surprisingly, the term temperature in this context enters into well-known academic texts.  For example, in the introductory section of Chinese Herbal Medicine: Materia Medica (1), a common text book in Western colleges, it is stated that:

The ‘Properties’ section in the main text of this book includes information about two major aspects of the medicinal substances.  One is the four qi.  In discussions about medicinal substances this term usually refers to the temperature characteristic....

Chinese writers who make reference to the Western texts in their works, as occurs in Chinese Materia Medica: Chemistry, Pharmacology, and Applications (2), end up adopting this terminology without comment: “The phrase ‘property’ refers to the temperature characteristics of Chinese herbs.”  “Property” is being used initially as the author’s reference to xing, which is an acceptable (if not the best) designation for xing, but then the words “temperature characteristics” ruin the presentation.

The “properties” of Chinese herbs, described as cold, cool, warm, and hot, are not descriptions of temperature despite the similarity in terms that have been selected to describe the nature of an herb and the temperature of a substance.  The temperature of herbs is room temperature; when we make a decoction, the temperature of the herbs reaches that of boiling water (100° C).  Gypsum has the same temperature as evodia whether the two are on the same shelf or in the same pot, even though they have markedly different natures, described as cold and hot, respectively.  This is not a matter of being picky about a term; rather it is an issue of properly understanding what is involved in describing the “nature” of an herb.

The use of the incorrect term temperature can lead to misconceptions, such as the idea that mixing a hot herb with a cold herb yields a neutral formulation, much in the way that hot water and cold water mixed together yield tepid water.  The idea that herbs have a characteristic defined as temperature can lead to confusion about the formulation principles that were used in making traditional prescriptions, and, thereby, influence the way in which one produces new formulas.  It can also mislead one when attempting to analyze the appropriate use of herbs and interpreting the responses of patients to consuming herbs.  

In traditional medical systems worldwide, the numerous effects of herbs were always summarized by placing them within in a small number of categories, each having a small number of divisions.  This limited categorization was an essential aspect of retaining information in early societies, in which herb knowledge was mainly passed on orally, requiring memorization, and where writing was difficult and not accessible to all in the manner we are used to today.  Limited categories are also important when the kind of detailed analysis of herbs, as done in modern laboratories, could not be made.  In China, the Shennong Bencao Jing (3), which long served as the model for written reporting about herbs, provided only a few characters to describe each herb.   An entry included the names of the herb, the type of environment where it could be found (e.g., mountains, valleys, or rivers), a brief description of its medical effects, and a summary of its nature in terms of two concepts: taste (wei; see: Taste and action of Chinese herbs...) and nature.   The nature of the herb was thus deemed an important aspect of how the herb would perform as a medicine.

There are two terms that the Chinese use to describe the nature of an herb: xing and qi.  Although these two terms are not directly interchangeable in meaning, they are both applied to the same underlying concept when it comes to herbal properties.   Most modern authors translate xing (or qi) as nature.  Thus, the nature of chrysanthemum is cool; the nature of atractylodes is warm. 

The Chinese character xing (see Figure 1) has two parts.  The main descriptive portion, which lends to the pronunciation, is sheng (see Figure 2), a commonly used character that depicts the growing of a plant (the bottom line is the earth; the vertical line is the stalk; the two horizontal lines along the stalk are leaves sprouted successively as the plant grows).  The term is used to designate birth, generation, and growth; it tends to suggest primordial qualities (rawness, newness, essential nature) and to emphasize vitality (vigor, activity):

Figure 1:  xing, in modern characters, comprised of the heart radical (xin) and the generation phonetic (sheng).	Figure 2:  sheng, the old version, right, shows a growing plant (the middle line is the extra one showing growth); the modern version relies on the standardized brush strokes.	Figure 3:  xin, the standard character; right is a depiction of the heart organ; the radical (category modifier) on the left is simplified; note the slight difference in stroke from Figure 1.

In front of the character for sheng is the radical (modifier) that means the same as xin (heart; see Figure 3).  Used as a modifier, it tends to mean inherent quality.  Put together, xin preceding sheng means the inherent direction of development.  In referring to people, xing captures the sense of a person’s nature, temperament, character, and personality.  It is what makes each person unique and what guides their actions in any given situation.  When referring to substances, such as herbs, it means their properties, essence, character, nature, and quality: what makes that substance unique and what determines the responses to it when used as a medicine. Thus, xing is the herb’s essence as applies toits potential for making changes, but not its temperature.

Qi, a term that is widely used in the descriptions of Chinese medicine, has a slightly different implication than xing, though it does sometimes also represent the idea of basic nature.  The qi of an herb, in the context of medicine, is more accurately described as its penetrating influence and has been described as the “odor” of the herb, suggesting its fragrant and penetrating potential.

The early effort to describe the nature (xing) of an herb as its qi was questioned by Gou Zongshi in the Bencao Yanyi (1119 A.D.).  He wrote that (4):

In the introductory section [of the Shennong Bencao Jing] it is written: “Drugs possess the five tastes—sour, salty, sweet, bitter, and acrid—and, in addition, the four qi: cold, hot, warm, and cool.”  I would like to examine the statement further.  Always, when the term qi is used, an odor is meant.  Cold, hot, warm, and cool are, however, the nature [xing] of drugs.  Thus, as the monograph on the common goose reads: “The fat of the white goose possesses cold xing.”  Cold qi would be impossible here, for it is, of course, the nature [xing] of drugs that is being discussed.  When the four qi are mentioned what is meant is aromatic-fragrant, putrid, penetrating, and strong-smelling.  There is no connection to cold, hot, warm, and cool.  If we take garlic, asafetida, dried fish, or sweating socks, as examples, their odor can be described as putrid.  The odor of the flesh of chickens, fish, duck, and snake can be termed penetrating.  The odor of kidneys, foxes, white horse penis, underwear attached to the genitals, as well as urinary sediments can be described as strong.  Finally, the odors of aquilaria, sandalwood, camphor, and musk can be characterized as aromatic.  In such cases, the use of the term qi is appropriate.  I fear that the character qi was mistakenly placed in the introductory sections later.  It should be changed to xing, which would correspond exactly.

In this description of qi as odor, Gou is relying on the original use of this term to depict a vapor (e.g., the steam in a rice pot).  In that sense, the cold or hot nature of an herb would not be properly described as its qi.

An example of an medical scholar who linked qi with odor is Zhang Chicong, in the Bencao Zhongyuan.  In describing the nature of all things in heaven and earth, he mentions that (4): “The qi are constituted by the five odors: penetrating, burnt, aromatic, strong, and putrid.”  He believed that the nature [xing] of things was the confluence of all the properties, categorized in fives according to the system of five elements: place of origin (geographical direction), season of development, color, odor, taste, etc.  Everything in fives; for herbs, that would mean that the properties [xing] of cold, cool, hot, and warm would be joined by neutral, as is common practice today.  Other authors maintained that the five tastes certainly fit the five element system, but thought that the nature of the herbs was part of the yin/yang system (which allows for an even number of designations: hot, warm, cool, cold).

Xu Dajun (5, 6) took yet another tact to distinguishing the herb’s xing from its other aspects,such as taste and qi.  “If a drug reaches the mouth, one can recognize its taste (wei); if it reaches the stomach, one can feel its nature (xing).” Its nature, as felt in the stomach, was different from its odor (or qi): “When drugs are used, they should be selected according to odor, taste, color, appearance, nature, time of genesis, or place of origin....”  This distinction between xing (nature) and qi (as odor) has not been followed by all subsequent writers, many of whom interchange xing and qi as terms to describe the nature of the herb.

The nature of herbs was originally described as sixing (four xing) or siqi (four qi).  The four designations were hot, warm, cool, and cold.  With hot and cold designations for the extremes of yang and yin respectively; there are intermediate designations of warm and cool, which are given to those herbs that have a moderate action.  Essentially, herbs that alleviated acute heat syndromes were designated cool or cold (depending on the intensity of their action), while those that alleviated acute cold syndromes were designated warm or hot.  For chronic disorders, the situation is entirely complex. 

A fifth category, of neutral or mild, has been added, yet, according to some authorities, all herbs fall into the basic four categories.  As stated in the Advanced Textbook on Traditional Chinese Medicine and Pharmacology (7), “Some drugs are not marked as cold or hot, and are considered mild drugs.  Actually, they must be slightly cool or slightly warm.  Therefore, the properties of all drugs fall into the four categories.”

A substance that is designated as having a hot nature will cause a burning sensation in the mouth (especially the tongue) when tasted and will also produce a burning sensation in the stomach when a quantity of it is ingested at once.  Secondarily, it will stimulate metabolism and alleviate feelings of chilliness.  Certainly, a hot drink of water (here, it is the temperature that is hot) will also do the same, though the effects will be of shorter duration.  Only a very small number of herbs, such as zanthoxylum, piper, and other “hot peppers,” (as we describe them), dry ginger, evodia, aconite, and a few other herbs are described as hot.

A substance designated as cold, however, will usually not cause a cold sensation in the mouth when tasted, and will usually not make a person feel chilly.  Rather, a cold substance will reduce a fever and thus take away a hot sensation that is part of a disease process.  When gypsum is administered to test animals, it will lower a fever but not lower the body temperature of an animal that lacks a fever.  The cold properties of herbs are determined by their ability to alleviate disease symptoms; they may also have adverse effects on digestion if the dosage is high enough or the duration of administration long enough.

As stated in the Advanced Textbook: “...in a hot case accompanied by such symptoms as high fever, irritability, and thirst, if the symptoms can be relieved by administering gypsum and coptis, we know that these drugs have cold properties.”  A cold substance may also quell the “digestive fire,” thus weakening some aspect of the digestive process if it is not in excess already, at least if taken for a long-enough period of time.  In modern terms, these cold substances may reduce hydrochloric acid levels (typical of the calcium-based minerals) or inhibit intestinal bacteria that are a part of the total digestive process (typical effect of the alkaloid-containing bitter, cold herbs).  Not all the cold or cool herbs adversely affect digestion; several herbs that have a warming quality can produce digestive system reactions in some users.  Short term use of “cold” natured herbs is not problematic for digestion. 

The nature and taste of an herb are not considered separate properties, but two intermingled qualities.  A spicy warm herb, such as perilla leaf, is not comprised of two component properties, as would be suggested by a temperature and a flavor, but, rather by a spicy-warm composite quality.  As such, all Materia Medica guides describe taste and nature together.  As stated in the Advanced Textbook: “When studying and identifying drug properties, qi and wei must not be separated.”  In traditional literature, the flavor is considered the yin aspect of the herbal property, while the qi or xing is considered the yang aspect of the herbal property; thus, they both reflect the nature of the herb, in terms of its basic essence and type of effect.

The nature of herbs is deemed one of the important aspects to be learned by all herbalists.  Liu Yiren, a famous herbalist of the 19th century, described the important herbs with the terms hot, warm, cold, and cool nature and concluded (8): “The above is an outline of medicinal natures: one should get it by heart as a secret art.”   Indeed, some Chinese authors felt that the nature (xing) of herbs included not only warming or cooling aspects, but whether they were supplementing or draining, and whether they had ascending or descending qualities, as described in the 1616 A.D. publication Shou Shi Pao Yuan by Gong Tingxian (4).  These are aspects of the herb that help define how it will be used without detailing the specific medical applications that have been developed for it.

In the Bencao Mengchuan, the following description of warming and cooling influences is presented:

Expert application of drugs is achieved if qi and taste are considered important.  The qi belong to heaven [the taste belongs to earth]; there are four such qi.  Warm and hot correspond to the yang qi of heaven; cold and cool correspond to the yin qi of heaven.  That which is yang rises; that which is yin descends....It is possible for one drug to have two or even three tastes or for there to be two qi combined within one drug.  If a strong hot qi and a weak cold qi are combined in one drug, the cold qi will not take effect as such.  If a strong cold qi and a weak hot qi are combined, the hot qi will not be detected as such.  If cold and hot qi are of equal proportions, the qi will appear warm.  In some cases, the warm qi is so distinct it appears to be hot; in other cases, the cool qi is so strongly developed it appears to be cold.  Careful distinctions must be made here.  In addition, if cold and hot qi are of equal proportions, the hot portion may be dominant when the drug is taken during the day and the effect will rise in the body; if the same drug is taken at night, the cold portion may dominate, and the effect will descend in the body.  On clear, bright days, the hot qi is decisive; on dark days the effects follow the cold qi.”

As this passage indicates, cold and hot qualities can coexist within an herb, they do not blend as would a temperature-type quality; the more extreme can dominate, or the two qi can manifest under different circumstances.  Thus, the cold or hot qi within the herb is said, by this author, to become manifest in accordance with the external qi: an herb can have a hot or cold influence depending on the environmental conditions when it is administered.  In like manner, when combining two herbs together in a formula, the hot and cold qi of individual herbs does not simply blend into something in-between; rather the hot and cold qualities are each present and may manifest differently according to the nature of the prescription and when it is given.  The same is true with the tastes, namely, combining tastes does not eliminate the individual tastes though one taste may ameliorate the extreme quality of another (such as sweet to help reduce the strong sense reaction to bitter).

Since the nature of herbs is listed in a small number of subdivisions (four or five), the designations are incomplete.  As noted by Jiao Shude (9): “aconite and dried ginger are hot-natured medicinals, but their heat is different; gypsum and coptis are both cold-natured medicinals, but their coldness is different…”

The nature of herbs is not fixed.  The nature of a plant material can be changed by traditional processing, which is viewed as a transformative function.  Ginseng, as collected, is cooling, but processed ginseng is warming; the same is true of rehmannia.  This change in nature illustrates the dependence of an herb’s nature on its interaction with man.   Beyond the effects of processing, the influence of the herbs will also depend on herb combining within formulas (see below), as well as the conditions within the body of the person consuming them and, in some cases, the environmental conditions when they are consumed.

In his book on combining herbs (10), Sionneau mentions combining herbs with opposite properties and is generally careful to avoid suggesting that when the herbs are used together they simply balance each other out.  Still, under the heading of combining the cold herb gypsum with the warm herb cinnamon twig, he proposes that this results in a decoction of cool nature.  In fact, cinnamon twig does not reduce the ability of gypsum to lower high fevers or to reduce stomach fire.  While gypsum may impede the ability of cinnamon twig to induce sweating, because of its astringent nature, it does not reduce the ability of cinnamon twig to warm the kidney, alleviate cold pain, and promote circulation.  It is possible to have a warm herb counteract or protect against specific influences of a cold herb, without losing its nature.  Still, it is more common to design formulas in such a way that two herbs act on different aspects of the individual’s constitution rather than to have them counteracting each other.  

There are a few commonly-cited traditional examples of herbs of extreme nature being combined in one formulation.  Examples are combining coptis and cinnamon bark and coptis and evodia.  These pairs were not designed to have one herb quellthe extreme nature of the other, but, rather, to have one herb alleviate a heat syndrome and the other alleviate a cold syndrome that coexists in an individual.  Thus, where coptis would purge heart fire, cinnamon bark would warm the kidney and help the fire settle in the lower warmer; together they treat mental agitation and insomnia.  Where coptis would purge heat in the stomach, evodia would disperse stagnant qi; together they treat nausea, vomiting, and acid reflux.  Generally, when one wishes to protect against an extreme nature of an herb, it is done by means other than using an herb of opposite nature.  For example, to protect the yin of the kidney from the hot spicy nature of aconite, cinnamon bark, or dry ginger, use of cooked rehmannia (which is warm in nature) is often the strategy employed.  Rehmannia nourishes the yin in order to provide the desired protective effects.  Similarly, when one wishes to protect the stomach from the cold nature of gypsum, oryza is often used.  Although oryza (sprouted rice) has a mildly warm quality, its warm nature is not the reason that it is selected for this particular role; rather the herb promotes appetite, harmonizes the spleen and stomach, and strengthens the spleen, doing so in a gentle manner which does not introduce other actions that are not desired (e.g., dispersing damp), which is why it is chosen for this role.

The idea that the nature of one herb would simply counteract the nature of another has been raised in the past.  Xu Dajun argued against this view (5), he said: “The fact is that drugs will always make full use of the potential associated with their nature.”

Herb properties may be transformed by the formulation strategy.  Jiao Shude gives an example of use of the herb schizonepeta (jingjie), which is utilized in formulas for both cold and heat type disorders: “When combined with siler (fangfeng) and perilla leaf (suye), it acts as a warm, acrid, exterior resolving medicinal, but when combined with mentha (bohe) and chrysanthemum (juhua), it acts as a cool, acrid, exterior resolving medicinal.”

When Chinese concepts that were developed in ancient times are depicted by terminology from a modern culture with a markedly different background, it is not uncommon for something to be lost in the translation.  In this case, because the mundane terms hot, warm, cool, and cold have been used as categories for the nature of herbs, the modern concept of temperature has been off-handedly applied to capture the meaning.  But, there are distinct differences between the concept the Chinese were putting forth in regard to an herb’s nature and the one which is broadly understood today as temperature.  Two results of this selection of an inappropriate term are the ideas that mixing cold and hot herbs yields a tepid intermediate, and that taking cold natured herbs can make a person feel chilly.  Neither of these notions were intended by the Chinese who wrote about the nature of herbs. 

1. Bensky D and Gamble A, Chinese Herbal Medicine: Materia Medica, 1993 rev. ed., Eastland Press, Seattle, WA.
2. Zhu Youping, Chinese Materia Medica: Chemistry, Pharmacology, and Applications, 1998 Harwood Academic Publishers, Amsterdam.
3. Yang Shou-zhong (translator), The Divine Farmer’s Materia Medica, 1998 Blue Poppy Press, Boulder, CO.
4. Unschuld PU, Introductory Readings in Classical Chinese Medicine, 1988, Kluwer Academic Publishers, Holland.
5. Unschuld PU, Forgotten Traditions of Ancient Chinese Medicine, 1990 Paradigm Publications, Brookline, MA.
6. Unschuld PU, Medicine in China: History of Pharmaceutics, 1986 University of California Press, Berkeley, CA.
7. State Administration of Traditional Chinese Medicine, Advanced Textbook on Traditional Chinese Medicine and Pharmacology, (4 vol.) 1995–6 New World Press, Beijing.
8. Yang Shouzhong (translator), The Heart Transmission of Medicine, 1997 Blue Poppy Press, Boulder, CO.
9. Sionneau P, Dui Yao: The Art of Combining Chinese Medicinals, 1997 Blue Poppy Press, Boulder, CO.
10. Jiao Shude, Ten Lectures on the Use of Medicinals, 2003 Paradigm Publications, Brookline, MA.

October 2010