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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 initial 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 symptoms of Gui Zhi Tang (Cinnamon Twig Decoction) for Taiyang Wind and Ma Huang Tang (Ephedra Decoction) for Taiyang Cold Damage.
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, pestilential qi, etc., through the skin and mucous membranes, 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 clinical treatment chaotic. Therefore, it is necessary to sort out its origins and standardize its concepts.
01
Concept of ‘Exterior Syndrome’ in Textbooks
Examining various editions of textbooks such as TCM Diagnosis, Exterior Syndrome is a fundamental concept with unique characteristics in TCM, yet there are many issues in understanding it.[1].
For example, the TCM Diagnosis published in August 2012[2] describes Exterior Syndrome in the section on 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, 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 is deep, it is called Interior Syndrome.
Exterior Syndrome refers to the initial stage of invasion by the six excesses, pestilential qi, etc., through the skin and mucous membranes, 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 throat, slight cough, shortness of breath, pale red tongue, thin coating, and floating pulse.
Based on the above concepts, 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 later states, “Generally, 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 they cannot be definitively classified as exterior.
Third, since it is a relative concept, it defines Exterior Syndrome as: “the initial stage of invasion by the six excesses, pestilential qi, etc., through the skin and mucous membranes, where the righteous qi resists the evil at the surface, primarily manifested by newly occurring aversion to cold and fever.” This definition does not reflect relativity and is also self-contradictory.
Fourth, according to the definition of Exterior Syndrome, the etiology is “the six excesses, pestilential qi, etc.,” and the characteristic is “newly occurring aversion to cold and fever.” However, not all invasions by the six excesses and pestilential qi are characterized by “aversion to cold and fever.”
02
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, stiffness and pain in the head and neck are also common in Exterior Syndrome but are not specific manifestations. 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; if floating, it indicates wind; if rapid, it indicates heat; if moving, it indicates pain; if rapid, it indicates deficiency; if there is headache and fever, slight sweating, and aversion to cold, it indicates 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, it indicates that the exterior has not been resolved; one should first resolve the exterior before attacking 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, abdominal fullness, and wheezing; if there is tidal fever, and if one wants to resolve it, one can attack the interior; if hands and feet sweat profusely, it indicates that the stool has become hard; Da Cheng Qi Tang is the main treatment; if sweating is excessive, with slight fever and aversion to cold, it indicates that the exterior has not been resolved; if the abdomen is large and full and not passing, one can use Xiao Cheng Qi Tang to harmonize the stomach qi, and do not let it lead to major diarrhea.”
Article 234 states: “In Yangming disease, the pulse is slow, with much sweating and slight aversion to cold; it indicates that the exterior has not been resolved; one can induce sweating, Gui Zhi Tang is appropriate.”
Article 152 states: “In Taiyang Wind, if there is diarrhea and vomiting, only when the exterior is resolved can one attack it. If the person has profuse sweating, with intermittent headache, fullness below the heart, pain in the hypochondrium, dry vomiting, shortness of breath, and sweating without aversion to cold, it indicates that the exterior has not been resolved and the interior is not harmonized; Shi Zao Tang is the main treatment.”
The original text above uses the presence or absence of “aversion to cold” as the basis for determining the existence of Exterior Syndrome.
03
Mechanism and Characteristics of Aversion to Cold
The mechanism of “aversion to cold” is that cold pathogens invade the body, binding the defensive qi, preventing it from “warming the flesh and distributing warmth.” Cold pathogens have the nature of constriction and stagnation, which binds the body’s defensive qi, leading to the occurrence of “aversion to cold.”
The characteristic of “aversion to cold” is that the patient feels cold, which is not alleviated by adding clothing or heating. If the patient feels cold, and adding clothing or heating alleviates it, then it is a characteristic of “fear of cold”; “fear of cold” is a manifestation of 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, with cold limbs, aversion to cold, and the pulse not palpable, if there is no agitation, it indicates death.”
Shang Han Lun also mentions “aversion to wind,” where the characteristic is that the patient feels cold when exposed to wind but not when not exposed; in TCM, this is described as “with wind, there is aversion; without wind, there is comfort.”
Although the patient only feels cold when exposed to wind, the characteristic of feeling cold when exposed to wind is the same as “aversion to cold,” meaning it is not alleviated by adding clothing or heating.
Thus, “aversion to wind” is a milder form of “aversion to cold,” and for this reason, Zhang Zhongjing does not strictly differentiate between the two, as seen in Article 12 of Gui Zhi Tang syndrome, which states “slight aversion to cold and slight aversion to wind” together; current textbooks often express this as “aversion to wind and cold.”
04
‘Exterior Syndrome’ is Not Caused by All Six Excesses
According to Shang Han Lun, Taiyang disease is Exterior Syndrome, characterized by “aversion to cold,” with the etiology of cold pathogens, and the mechanism of “aversion to cold” is that cold pathogens bind the defensive qi, preventing it from warming the flesh. The treatment for Taiyang disease includes two formulas, namely Ma Huang Tang and Gui Zhi Tang.
Ma Huang Tang and Gui Zhi Tang are effective in dispersing cold and are representative formulas for resolving the exterior in current Formulas studies, targeting the etiology of cold pathogens.
It is evident that Exterior Syndrome can only be caused by cold pathogens, not by the “six excesses, pestilential qi, etc.” as stated in TCM Diagnosis [2].
Only cold pathogens have the nature of constriction and stagnation, which can bind the body’s defensive qi, leading to the occurrence of “aversion to cold.” Other pathogenic factors (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 inflammatory and rising nature, it will not bind the body’s defensive qi, so invasion by heat pathogens will not present “aversion to cold.” Shang Han Lun Article 6 states: “In Taiyang disease, if there is fever and thirst, and no aversion to cold, it indicates a warm disease.”
In the Discussion on Warm Diseases, Upper Jiao section, Article 4 states: “Taiyin Wind Warm, Warm Heat, Warm Pestilence, Winter Warm, if there is initial aversion to wind and cold, Gui Zhi Tang is appropriate. But if there is aversion to heat and no aversion to cold, and thirst, Yin Qiao San is appropriate.”
Zhang Zhongjing clearly states that warm diseases do not present aversion to cold in the early stages.
Wu Jutong proposed two formulas for the early stage of warm diseases: 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 a warm disease but Taiyang Wind; Yin Qiao San syndrome is indeed the early stage of warm disease, which is caused by heat pathogens and does not present aversion to cold.
2. Wind Pathogens
Wind pathogens are “external pathogens with characteristics of movement and lightness”[3], and due to their nature of movement and lightness, they will not bind the body’s defensive qi, so invasion by wind pathogens will not present “aversion to cold.”
Through my research, I have found that “wind pathogens” are not specific causes, and most of the time refer to external pathogens; in rare cases, they are considered as mild forms of cold pathogens, such as in 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, dryness pathogens can indeed cause “aversion to cold,” as their astringent nature can bind the defensive qi. Therefore, to prove their astringent nature, dryness pathogens 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” mentioned 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 treatment for cool dryness is Xing Su San (Apricot Kernel and Perilla Leaf Powder), which consists of herbs that disperse cold and resolve phlegm, and has nothing to do with dryness.
4. Dampness Pathogens
Dampness pathogens are “external pathogens with characteristics of heaviness, stickiness, and downward tendency”[2], and due to their heaviness and stickiness, they can indeed bind the defensive qi, preventing it from warming the flesh, thus can present “aversion to cold.” “Aversion to cold” is a characteristic manifestation of the initial stage of dampness invasion.
The deeper theoretical basis is that dampness is similar to water, and water is inherently cold. Therefore, “dampness” shares many characteristics with “cold.” At the same time, the methods for dispersing cold and dampness are also 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 of “heat”[4], the original meaning of “heat” is “hot.”
However, from clinical practice, “heat” is a special manifestation of “warmth.”
First, it has seasonality, meaning “the disease of warmth occurs before the summer solstice, while 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 stage of general heat invasion is in the lungs, known as “warm pathogens first invade the lungs,” presenting as Yin Qiao San syndrome or Sang Ju Yin syndrome; while the initial stage of heat invasion is in Yangming, known as “summer heat arises from Yangming,” presenting 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 both heat and dampness; thus, it is sometimes referred to as “summer damp heat.”
Therefore, in the current six excesses of pathogenic factors, “heat” should be classified under “warmth” and does not need to be listed separately.
If heat carries dampness, then “aversion to cold” can be seen; clearly, the cause of “aversion to cold” is dampness, not heat.
In Formulas, Xiang Ru San (Elsholtzia Powder) is used as a remedy for heat, which is contradictory, as heat is inherently hot; how can a hot remedy be used to resolve heat?
Xiang Ru San is actually used to treat cases where cold pathogens are contracted during the summer, known as “using Xiang Ru in summer is like using Ma Huang in winter.”
05
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 initial 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
Note: The original text was first published in Chinese Journal of Traditional Chinese Medicine, 2015, 30(7): 2322~2324.
The cover image is sourced from Shetu Network.
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