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Exterior syndrome (Biao Zheng) is one of the most common concepts in Traditional Chinese Medicine (TCM), originating from Zhang Zhongjing’s “Shang Han Lun” (Treatise on Cold Damage).
In “Shang Han Lun”, exterior syndrome refers to Taiyang disease, which is the early stage of invasion by cold pathogens, characterized by “floating pulse, stiffness and pain in the head and neck, and aversion to cold”. Based on this, it is differentiated into the Gui Zhi Tang syndrome of Taiyang wind and the Ma Huang Tang syndrome of Taiyang cold damage according to the presence or absence of sweating.
In “Shang Han Lun”, the concept of exterior syndrome is clear and standardized.
However, in current textbooks, the concept of exterior syndrome is defined as: “the initial stage of invasion by the six excesses, pestilence, and other evils, where the righteous qi resists the evil at the surface, primarily manifested by newly occurring aversion to cold and fever.”
Clearly, textbooks have expanded the scope of “exterior syndrome”, and the concepts in current textbooks are not standardized, making it difficult to justify and leading to confusion in clinical treatment. Therefore, it is necessary to sort out its origins and standardize its concept.
1. The Concept of “Exterior Syndrome” in Textbooks
Examining various editions of textbooks such as “TCM Diagnosis”, exterior syndrome, as a fundamental concept unique to TCM, has many issues in understanding.[1] For example, the “TCM Diagnosis” published in August 2012 describes exterior syndrome in the section on the differentiation of the eight principles.
Exterior and interior are two principles for distinguishing the location of disease, whether external or internal, superficial or deep. Exterior and interior are relative concepts; for instance, skin is exterior while muscles and bones are interior; organs (Zang) are interior while bowels (Fu) are exterior; meridians are exterior while organs are interior; among the three Yang meridians and three Yin meridians, the Yang meridians are exterior while the Yin meridians are interior, etc.
Generally speaking, the skin and muscles are external and belong to the exterior; blood vessels, bone marrow, and organs are internal and belong to the interior. However, in clinical differentiation, when an external pathogen invades the muscle surface and the disease is superficial, it is called exterior syndrome; when the disease is in the organs and deep, it is called interior syndrome.
Exterior syndrome refers to the initial stage of invasion by the six excesses, pestilence, and other evils, where the righteous qi resists the evil at the surface, primarily manifested by newly occurring aversion to cold and fever. Clinical manifestations include newly occurring aversion to wind and cold, or aversion to cold and fever, pain in the head and body, sneezing, nasal congestion, runny nose, itchy and painful throat, slight cough, shortness of breath, pale red tongue, thin coating, and floating pulse.
Based on the above concept, some issues can be identified.
First, exterior and interior are relative concepts, meaning that any syndrome can be classified as either exterior or interior.
Second, since it is a relative concept, it is contradictory to later state, “Generally speaking, the skin and muscles are external and belong to the exterior; blood vessels, bone marrow, and organs are internal and belong to the interior.” This is self-contradictory because the skin and muscles also have relativity, so it cannot be definitively classified as exterior.
Third, since it is a relative concept, defining exterior syndrome as: “the initial stage of invasion by the six excesses, pestilence, and other evils, where the righteous qi resists the evil at the surface, primarily manifested by newly occurring aversion to cold and fever” does not reflect relativity and is also self-contradictory.
Fourth, according to the definition of exterior syndrome, the etiology is “the six excesses, pestilence, and other evils”, and the characteristic of exterior syndrome is “newly occurring aversion to cold and fever”. However, not all invasions by the six excesses and pestilence are characterized by “aversion to cold and fever”.
2. The Origin of the Concept of “Exterior Syndrome”
The concept of “exterior syndrome” originates from “Shang Han Lun”, where Taiyang disease is exterior syndrome. “Shang Han Lun” is currently the primary literature for studying “exterior syndrome”.
The outline of Taiyang disease is stated in the first line: “In Taiyang disease, the pulse is floating, there is stiffness and pain in the head and neck, and aversion to cold”.
The floating pulse, stiffness and pain in the head and neck, and aversion to cold mentioned in the original text are common clinical manifestations of exterior syndrome. However, only “aversion to cold” is specific, meaning that only “aversion to cold” is a characteristic manifestation of exterior syndrome.
Floating pulse and stiffness and pain in the head and neck are also common in exterior syndrome but do not belong to the specific manifestations of exterior syndrome. In other words, while these manifestations are common in exterior syndrome, they are not exclusive to it.
Therefore, the key to determining whether it is exterior syndrome is the presence or absence of “aversion to cold”. That is to say, “where there is one part of aversion to cold, there must be one part of exterior syndrome”, or it can be considered that “there is one part of aversion to cold, and thus there is one part of exterior syndrome”.
In “Shang Han Lun”, Article 134 states: “In Taiyang disease, the pulse is floating and rapid; floating indicates wind, rapid indicates heat, and movement indicates pain. Rapid indicates deficiency; headache and fever, slight sweating, and aversion to cold indicate that the exterior has not been resolved.”
Article 164 states: “After a major purge in cold damage, if sweating recurs, and there is fullness below the heart and aversion to cold, the exterior has not been resolved; one should not attack the fullness but first resolve the exterior. Only after resolving the exterior can one attack the fullness. To resolve the exterior, Gui Zhi Tang is appropriate; to attack the fullness, Da Huang Huang Lian Xie Xin Tang is appropriate.”
Article 208 states: “In Yangming disease, the pulse is slow; even if sweating occurs, if there is no aversion to cold, the body must be heavy, with shortness of breath, fullness in the abdomen, and wheezing. If there is tidal fever, one may want to resolve the interior. If hands and feet sweat profusely, this indicates that the stool is hard. Da Cheng Qi Tang is the main treatment; if sweating is excessive with slight fever and aversion to cold, the exterior has not been resolved; if there is fullness in the abdomen, one may use Xiao Cheng Qi Tang to harmonize the stomach qi, and do not allow it to lead to major diarrhea.”
Article 234 states: “In Yangming disease, the pulse is slow, and if there is much sweating with slight aversion to cold, the exterior has not been resolved; one may induce sweating, and Gui Zhi Tang is appropriate.”
Article 152 states: “In Taiyang wind, if there is diarrhea and vomiting, one can only attack after the exterior is resolved. If the person sweats profusely, has headaches, fullness below the heart, pain in the hypochondrium, dry vomiting, shortness of breath, and sweats without aversion to cold, this indicates that the exterior has not been resolved and the interior is not harmonized; Shi Zao Tang is the main treatment.”
The original text indicates that the presence or absence of “aversion to cold” is the basis for determining whether there is exterior syndrome.
3. The Mechanism and Characteristics of Aversion to Cold
“Aversion to cold” is caused by the invasion of cold pathogens, which bind the defensive qi, preventing it from “warming the flesh and dividing the meat”. Cold pathogens have the nature of constriction and stagnation, which binds the body’s defensive qi, leading to the sensation of “aversion to cold”.
The characteristic of “aversion to cold” is that the patient feels cold and is not relieved by adding clothing or heating. If the patient feels cold and is relieved by adding clothing or heating, this is a characteristic of “fear of cold”, which indicates Yang deficiency.
It is important to note that in “Shang Han Lun”, Zhang Zhongjing does not distinguish between “aversion to cold” and “fear of cold”, referring to the cold sensation in the Si Ni Tang syndrome as “aversion to cold”, as seen in Article 298: “In Shaoyin disease, if there is cold aversion and the body curls up, the pulse is absent, and there is no agitation but restlessness, this indicates death.”
“Aversion to wind” is also mentioned in “Shang Han Lun”; its characteristic is that the patient feels cold when exposed to wind but not when not exposed to wind. In TCM, this is described as “with wind, there is aversion; without wind, there is peace”.
Although the patient only feels cold when exposed to wind, the characteristics of feeling cold in the wind are the same as “aversion to cold”, meaning it is not relieved by adding clothing or heating. Therefore, “aversion to wind” is a milder form of “aversion to cold”. Because of this, Zhang Zhongjing does not strictly differentiate between the two; for example, in Article 12, the Gui Zhi Tang syndrome is described as “slight aversion to cold and slight aversion to wind”.
4. “Exterior Syndrome” Is Not Caused by All Six Excesses
According to “Shang Han Lun”, Taiyang disease is exterior syndrome, characterized by “aversion to cold”. The etiology of “aversion to cold” is cold pathogens, and the mechanism of “aversion to cold” is that cold pathogens bind the defensive qi, preventing it from warming the flesh. There are two formulas for treating Taiyang disease, namely Ma Huang Tang and Gui Zhi Tang.
Both Ma Huang Tang and Gui Zhi Tang have the effect of dispersing cold and are currently representative formulas for resolving the exterior in “Formulas and Herbs”, targeting the etiology of cold pathogens.
It can be seen that exterior syndrome can only be caused by cold pathogens, not by the “six excesses, pestilence, and other evils” as stated in “TCM Diagnosis”.
Only cold pathogens have the nature of constriction and stagnation, which can bind the body’s defensive qi, leading to “aversion to cold”. Other evils (except dampness) cannot cause exterior syndrome, especially heat pathogens.
1. Fire (Heat) Pathogens
Fire (heat) is an “external pathogen with characteristics of inflammation and heat rising”[2], and due to its characteristics of inflammation and heat rising, it will not bind the body’s defensive qi, so invasion by fire pathogens will not lead to “aversion to cold”. Article 6 of “Shang Han Lun” states: “In Taiyang disease, if there is fever and thirst, and no aversion to cold, this indicates a warm disease.”
In the “Warm Disease Differentiation”, the section on the upper jiao states: “In Taiyin wind warmth, warm heat, warm pestilence, and winter warmth, if there is initial aversion to wind and cold, Gui Zhi Tang is appropriate. However, if there is aversion to heat and no aversion to cold with thirst, the cooling and mild formula Yin Qiao San is appropriate.”
Zhang Zhongjing clearly states that in the early stage of warm disease, there is no aversion to cold. Wu Ju Tong proposed two formula syndromes for the early stage of warm disease: Gui Zhi Tang for aversion to wind and cold, and Yin Qiao San for no aversion to cold. Gui Zhi Tang syndrome is certainly not warm disease but Taiyang wind; Yin Qiao San syndrome is the early stage of warm disease, which is caused by heat pathogens and does not have aversion to cold.
2. Wind Pathogens
Wind pathogens are “external pathogens with characteristics of movement, lightness, and dispersion”[3], and due to their characteristics of movement, lightness, and dispersion, they will not bind the body’s defensive qi, so invasion by wind pathogens will not lead to “aversion to cold”.
Through my research, I have found that “wind pathogens” are not specific causes; most of the time, they refer to external evils, and occasionally they refer to mild cases of cold pathogens, such as in the Gui Zhi Tang syndrome of “wind stroke”.
3. Dryness Pathogens
Dryness pathogens are “external pathogens with characteristics of dryness and astringency”[2]. Based on this concept, invasion by dryness pathogens may indeed lead to “aversion to cold”, as the astringent nature can bind the defensive qi. Therefore, to prove their astringent nature, dryness syndromes are divided into warm dryness and cool dryness. “Cool dryness” often has aversion to cold and fever, no sweating, headache, and a floating tight pulse.[2]
In fact, dryness only has the characteristic of “dryness”; the “astringency” referred to here is actually the “constriction” nature of cold pathogens.
“Aversion to cold and fever, no sweating, headache, and a floating tight pulse” are typical characteristics of cold pathogens binding the muscle surface; the formula for treating cool dryness is Xing Su San (Apricot Kernel and Perilla Leaf Powder), which consists of herbs that resolve the exterior, disperse cold, and clear phlegm, and has no relation to dryness.
4. Damp Pathogens
Damp pathogens are “external pathogens with characteristics of heaviness, stickiness, and downward tendency”[2]. Due to their heaviness and stickiness, they can indeed bind the defensive qi, preventing it from warming the flesh, thus leading to “aversion to cold”. “Aversion to cold” is an inherent manifestation of the initial stage of invasion by damp pathogens.
The deeper theoretical basis is that dampness is similar to water, and water is inherently cold. Therefore, “dampness” has many characteristics similar to “cold”. At the same time, the methods for dispersing cold and dampness are similar, and certain herbs such as Cang Zhu (Atractylodes) and Bai Zhi (Angelica Dahurica) can disperse both dampness and cold.
5. Heat Pathogens
Heat pathogens are “external pathogens with characteristics of heat, rising, and combined dampness”[3].
According to Mr. Li Jinyong’s research on the character “heat”[4], the original meaning of “heat” is “hot”.
However, from clinical practice, “heat” is a special manifestation of “warmth”.
First, it has seasonality, i.e., “the disease of warmth occurs before the summer solstice, and the disease of heat occurs after the summer solstice”; “heat” only occurs in summer.
Second, heat is heavier in degree than heat at other times, known as “extreme summer heat”; clinically, the initial invasion of general heat pathogens is in the lungs, i.e., “warm pathogens first invade the lungs”, manifested as Yin Qiao San syndrome or Sang Ju Yin syndrome; the invasion of heat pathogens is initially in Yangming, known as “summer heat arising from Yangming”, manifested as Bai Hu Tang syndrome.
Third, heat often carries dampness. In summer, due to hot weather, the evaporation of surface water vapor increases the humidity in the air, creating a damp and hot environment, leading to diseases that often present with both heat and dampness, hence the term “summer heat”.
Therefore, in the current classification of the six excesses, “heat” should be classified under “warmth” and does not need to be listed separately.
If heat carries dampness, then “aversion to cold” may be seen, but clearly, the cause of “aversion to cold” is dampness, not heat.
In “Formulas and Herbs”, the formula Xiang Ru San (Elsholtzia) is used as a remedy for heat, which is contradictory, as heat is inherently hot, and all the herbs in Xiang Ru San are warm and spicy; how can one resolve heat with heat?
Xiang Ru San is actually used to treat conditions where cold pathogens are encountered in summer, known as “using Xiang Ru in summer is like using Ma Huang in winter”.
5. Definition of Exterior Syndrome
Based on the above analysis, exterior syndrome can be defined as: exterior syndrome is a clinical syndrome characterized by aversion to cold in the early stage of invasion by cold pathogens. Common clinical manifestations of exterior syndrome include stiffness and pain in the head and neck, floating pulse, pale tongue, and thin white coating. Based on the presence or absence of sweating, it can be divided into Taiyang wind exterior deficiency syndrome and Taiyang cold damage exterior excess syndrome.
References:
[1] Liu Yingfeng, Wu Ke, Huang Bo. Unified Classification of Exterior Syndrome, Bridging the Differentiation Principles: Theoretical Questions. Chinese Journal of Traditional Chinese Medicine, 2014, 29(7): 2093-2096
[2] Li Candong, Wu Chengyu. TCM Diagnosis. 3rd Edition. Beijing: China Traditional Chinese Medicine Press, 2012: 141-143, 156
[3] Sun Guangren, Zheng Qixin. Foundations of TCM. 3rd Edition. China Traditional Chinese Medicine Press, 2012: 207, 209-211
[4] Li Jinyong. On the Formation of the Six Excesses Theory in Traditional Chinese Medicine. New Medical Communications, 1979(S1): 1-2
Originally published in the “Chinese Journal of Traditional Chinese Medicine” 2015, 30(7): 2322-2324.
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