Six External Pathogens
In the view of TCM , health is a state in which the relations of the components of the human body and the unity between man and nature are kept in harmony. When this harmony is destroyed by certain factors and the body cannot maintain its normal state , disease occurs. So , any factors that destroy the relative balance of the human body are known as causes of disease in TCM.
Etiology in TCM is characterized by three points : First, recognizing etiologic factors under the guidance of the Concept of Holism. Unlike Western medicine, TCM does not emphasize the identification of the specific etiologic factors such as viruses and bacteria of diseases. Instead, it stresses the significance of the environmental or internal conditions of the human body in the occurrence of disease. For example, man depends on the supply of both Heaven Yang and Earth Yin, which affect the human body through different climatic conditions and food and drink. Therefore , abnormal changes of the weather or climatic conditions are regarded as one of the major groups of pathogenic factors that invade the body from the outside; and improper diet , such as excessive or inadequate intake of food, or preference for food of certain tastes , are pathogenic factors that directly disturb the functional activities of the Zang and Fu Organs.
In addition, emotional stress, if in excess, may also become a pathogenic factor as it will lead to dysfunction of the Zang and Fu Organs.
Second, stressing the relativity of pathogenic factors. Whether or not abnormal changes of any factors, such as climatic conditions or emotional changes, can transform into pathogenic factors depends not only on the changes themselves , but also the reaction of the human body to these changes. For example, a sudden and violent climatic change may become one of the Six External Pathogens , but if its effect is limited for some reason, or the resistance of the body is strong enough to defend the body, it will not cause diseases. In such conditions ,it cannot be regarded as one of the Six External Pathogens. Abnormal changes of weather provide the possibility for climatic conditions to become pathogens, but it is the mutual action of the climatic conditions and Vital Qi that determines whether the abnormal weather transforms into a pathogen or not.
Third, identifying pathogenic factors by analyzing the manifestations of a disease. TCM believes that any syndrome is a morbid reflection of the human body under the action and influence of pathogenic factors. There is a correspondence between the pathogens and the manifestations of disease. Therefore, when analyzing causes of a disease, apart from possible objective considera- tions , TCM deduces the nature of the pathogens mainly on the basis of the manifestations. For example, when a patient has fever and chills, lack of sweat, stuffy and running nose and a floating tense pulse, he can be diagnosed as having an Exterior Syndrome due to Wind Cold. Whether or not it is very cold during the occurrence of the disease is not very important in the determination of the pathogens.
This is a general term for Wind, Cold, Summer Heat, Damp, Dryness and Fire. The six kinds of climatic changes in excess, which usually invade from outsidethe body to cause diseases. They are transformed from the six kinds of climatic changes, which, in normal conditions, are the basic conditions for the survival of the human being. In the long period of evolution, man has gradually developed the ability to adapt himself to the changes of weather. However, when these changes are excessive and go beyond the adaptability of the human body, they may disturb the functional activities of the human body, turning into pathogenic factors. As they invade the human body from the outside, diseases caused by them are referred to as External diseases. Generally speaking , the Six External Pathogens have the following common characteristics:
First , invasion
of the Six External Pathogens into the human body is closely related to
the climatic conditions in different seasons and the environment one lives
in. Diseases related to Wind occur more frequently in spring because Wind
is prevalent in this season. Summer Heat attacks the body only in the
summer because it exists only in this season. Living for a long time in
a damp place, one is likely to suffer from arthritis. And working in a
hot environment, one is liable to be invaded by Heat and Fire.
Fourth, the Six External Pathogens can act not only on one another in the occurrence of diseases, but can transform into each other in accordance with the constitution of an individual. As a result, the nature of the disease's pathogenesis and Syndrome changes accordingly. For example, Cold may transform into Heat due to the Yang Excess constitution of a patient when it invades from the Exterior to the Interior; while Damp, in the case of interlocking in the interior of the body and obstructing the distribution of Body Fluids, may be transformed into Dryness.
1. Pathogenic Wind
Wind prevails in spring, but it also exists all the year round. So diseases caused by Wind can be seen in all four seasons. Wind in excess is known as pathogenic Wind, which serves as the most important External pathogen and usually invades the human body by attacking the superficial muscles and skin first. Pathogenic Wind possesses the following features: First, wind is air in motion. Being a pathogen of Yang nature, Wind tends to cause loose striae of muscles, and disease caused by Wind usually occurs in the upper body. As Wind is mobile, going upwardand outward, it is a yang pathogen. When it attacks the body, it tends to attack the superficial muscles, the Yang Channels and the upper part of the body. So, Wind often causes such symptoms as sweating and hesdache.
Second, wind has the property of moving and changing. This means that Wind is mobile in nature and it may cause shaking of trees. So diseases caused by Wind are characterized by their migratory symptoms, sudden onset, and rapid progression. For example, rheumatic arthralgia caused mainly by pathogenic Wind is marked by migratory pain of the joints, and urticaria, which is due to invasion of pathogenic Witid, is marked by migratory itching of the skin and its intermittent occurrence. Third , wind is the predominant pathogen. As Wind exists all year round, it can cause diseases whenever the defensive ability of the body declines. Therefore, a great variety of diseases are related to the invasion of Wind. Furthermore, as Wind is in a state of constant motion and tends to cause loose striae of muscles, other pathogens usually attack the human body following the invasion of pathogenic Wind. So external diseases are usually ascribed to pathogenic Wind or Wind in combination with other pathogenic factors.
2. Pathogenic Cold
Cold is prevalent in winter. It usually attacks the body when the temperature is low and man fails to adapt himself to the change by dressing properly. Pathogenic Cold may attack the Exterior of the body or invade the interior of the body directly. Diseases in the former case are called affliction pf pathogenic Cold, and those in the latter case, direct attack of Cold on the interior.
Pathogenic Cold has the following features:
First, being a Yin pathogen, Cold tends to impair Yang Qi. Cold is the prevalent climate in winter, in which Yin Qi of nature is flourishing, so it is a Yin pathogen. Like attracts like. So Yin of the body will become hyperactive in the case of invasion of Cold and Yang Qi is overrestricted. For example, Cold attacking the Exterior often obstructs Defensive Qi (one kind of Yang Qi), leading to failure of the Exterior to be warmed and resultant chills. Direct attack of Cold on the Spleen and Stomach usually cause Cold pain in the abdomen, watery diarrhea, etc. , meaning that Spleen Yang is impaired and its transforming and transporting actions are disturbed.
Second, cold is liable to cause coagulation of Blood and retention of Body Fluids. Blood and body fluids depend on the propelling effect of Yang Qi and a moderate temperature for their free circulation. If Cold invades the body, Yang Qi will be impaired and body temperature will be lowered. So the flow of Blood and Body Fluids will become sluggish, or even coagulated, which is clinically marked by pain. For example, rheumatic arthralgia mainly due to pathogenic Cold is marked by Cold pain of the joints, which is usually severe and fixed.
Third, contracting nature of Cold. This means that pathogenic Cold often leads to ingoing of Qi , contraction of the muscular striae and convulsion of tendons and vessels. If attacked by pathogenic Cold, the muscular striae and the sweat pores will be closed, so Defensive Qi will be obstructed, and fever or chills and absence of sweating will occur as a result. Invasion of patbogenic Cold into the vessels will cause coagulation of Qi and Blood and contraction of the vessels, leading to headache, pantalgia, tense pulse, etc. Inability of the limbs to flex and extend freely or Cold and numbness of the limbs will follow if the Cold attacks the Channels and joints and results in contraction of the tendons and Channels.
3. Pathogenic Summer Heat
Summer Heat is a pathogen existing only in summer. So diseases caused by it are also seen only in summer and are obviously seasonal. Summer Heat results from the hot climate in this season dueto the exuberance of Yang Qi in nature.
Summer Heat has the following characteristics:
First, as a Yang pathogen, Summer Heat has a scorching nature. Summer Heat derives from overabundant Yang Heat in summer, so when it attacks the body, Yang Qi of the body will be extremely exuberant. For this reason, diseases caused by Summer Heat are usually manifested as excessive Heat symptoms such as high fever, dysphoria, a red face, full and large pulse.
Second, going upward and dispersing, Summer Heat tends to consume Qi and Body Fluids. When Summer Heat invades the body, it often leads to opening of the sweat pores, therefore profuse sweating results. Meanwhile, excessive Yang due to attack of Summer Heat will also consume Yin Fluids. So Deficiency of Body Fluids occurs. Because of the excessive discharge of Body Fluids, Qi will escape at the same time, which is known as escape of Qi following discharge of Body Fluids. Besides, hyperactivity of the body, with Qi as the motive force of the activities, will also cause Deficiency of Qi. Therefore, invasion of Summer Heat is also marked by the symptoms of Deficiency of both Qi and Yin, such as thirst with desire for drinks, scanty and dark urine, shortness of breath, lassitude, or even sudden syncope and coma.
Third, summer Heat often invades the body in combination with Damp. Summer is both hot and rainy, and people usually take more cold food and beverages; tberefore, Damp is also a common factor contributing to diseases in summer. In such cases, there is latent moderate fever, latent sweating, thirst with little fluid intake, dusky and greasy face, heaviness of body, lassitude, depressed feeling over the chest, nausea, vomiting, and loose stools.
4. Pathogenic Damp
Damp prevails in long summer, a season in which Yang Qi begins to decline and Yin Cold begins to rise. So water and Damp exist everywhere. Diseases caused by Damp can be divided into two types, Internal Damp and External Damp. The former is mostly caused by a wet climate, living in a damp place or being caught by rain, the latter by retention of water in the interior due to dysfunction of the Spleen, or excessive intake of cheese , alcohol, and raw and cold food.
Pathogenic Damp has the following features:
First, being a Yin pathogen, Damp tends to obstruct the flow of Qi and to impair Yang Qi. Damp, heavy and turbid in nature, is similar to water, so it belongs to Yin. As a substantial Yin pathogen, Damp is most likely to obstruct the flow of Qi when it stays in Zangfu Organs or Channels, giving rise to disturbance of the ascent and descent of Qi, or blockage of the Channels. Clinically this is mainly marked by chest fullness, an oppressed feeling in the epigastric region, scanty and difficult urination, sticky stools, abdominal pain, tenesmus, etc. Damp depends on Yang Qi for movement; when it invades the body, it will impair Yang Qi, especially Spleen Yang, leading to Kiarrhea, oliguria, edema, etc.
Second, Damp has a turbid and heavy nature. Damp tends to lead to a heavy feeling of the head as if being bound, soreness and aching of the whole body, and lassitude and heaviness of the limbs. This is because Damp is a Yin pathogen that is apt to lodge in the Channels and obstruct the flow of Qi. For example, an attack of pathogenic Damp on the superficial muscles will be manifested by heaviness of the head due to obstructed lucid Yang being unable to reach the head; obstruction of Yang Qi in the joints and Channels by Damp often gives rise to numbness of the muscles and skin and pain and heaviness of the joints, which is also referred to as Damp arthralgia. By the turbid nature of Damp is meant that pathogenic Damp often brings about dirty and turbid excretions, a dirty face, loose and mucous stools, bloody and purnlent stools, turbid urine. leukorrhea, eczema with excessive exudate.
Third, Damp is marked by viscosity and stagnation. Damp is thickened water, so it is sticky in nature. For this reason, diseases caused by Damp are characterized by their lingering course and are difficult to cure. Even when they are temporarily relieved, they are liable to reattack, as usually seen in eczema and arthralgia due to Damp. Besides, diseases due to Damp often exhibit sticky symptoms such as slimy and greasy stools and urine, and greasy fur of the tongue.
Fourth, Damp tends to flow downward and to attack the lower portion of the body. As Damp is similar to water in nature, it has a tendency to go downward. So diseases caused by Damp are often marked by symptoms in the lower portion of the body, such as edema, which occurs mostly in the legs, strangury, leukorrhea, diarrhea and dysentery.
5. Pathogenic Dryness
Dryness is prevalent in autumn, a season caused by decline of Yang Qi in nature in which everything becomes astringent. If it is excessive, it will cause diseases. In eariy autumn, Dryness often attacks the human body in combination with Heat, because summer Heat has still not abated completely. In such cases, it is called warm Dryness, while in the autumn, it usually attacks the body together with Cold, because winter cold is coming. In such cases, it is known as Cold Dryness.
Pathogenic Dryness has the following features:
First, pathogenic Dryness, which is dry in nature, tends to impair Body Fluids. As Dryness is the opposite of moisture, it is liable to injure Body Fluids, leading to dry symptoms as a result of loss of moisture in organs and tissues, such as a dry nose and mouth, a dry throat accompanied by thirst, lusterless hair, dry or even cracked skin, scanty urine and dry stools.
Second, pathogenic Dryness impairs the Lung first. The Lung is a delicate organ which means it is easily impaired by pathogens. Under normal conditions, the Lung desires moistening and is disgusted at Dryness, so Dryness tends to impair the Lung. In addi- tion, the Lung corresponds to autumn according to the Five Elements theory, so Dryness affects the Lung more frequently at that time. Furthermore, the Lung commumcates with the environment directly through the nose, and Dryness usually enters the body through the nose, thus the Lung is the first organ to be affected in the case of invasion of pathogenic Dryness. Impaired by pathogenic Dryness, Lung Yin or Body Fluids in the Lung will become deficient and ascent-descent of Lung Qi will be disturbed, giving rise to a dry cough with little sputum, or thick sputum which is very difficult to expectorate, dry nose and skin, or even sputum mixed with blood, and chest pain associated with shortness of breath.
6. Psthogenic Fire (Heat)
Pathogenic Heat, Fire and warmth all arise from overabundance of Yang Qi. They are of the same nature but their degree is different. Fire is advanced Heat, while Heat is advanced warmth. Pathogenic Heat and warmth are usually caused by External pathogens such as External pathogenic Wind Heat and pathogenic Warm Heat while Fire can be caused by either an attack of External pathogens or excessive Yang Qi of the body, such as Fire transformed from extreme External pathogenic Heat or from stagnant Damp, Heart Fire and Liver Fire.
Fire as one of the Six External Pathogens actually refers to External Heat. The term "Fire" is often used to refer to External pathogenic Heat. Pathogenic Fire (Heat) is clinically characterized as follows
First, being a Yang pathogen, it tends to flare up. Fire results from excessive Yang, so it is a Yang pathogen. Besides, Fire has the properties of going upward and of being hot. Therefore, Syndromes due to an attack of Fire are marked by high fever, aversion to heat, severe thirst, profuse sweating, full and rapid pulse, red face and eyes, redness on the tongue tip or edges, oral ulcers, swollen and painful gums, etc.
Second, fire is liable to consume both Qi and Yin Fluids. Being the result of Excess Yang, Fire often forces Body Fluids to be discharged profusely and directly impairs Yin Fluids, so impairment of Yin is frequently seen in diseases caused by Fire. Fire can consume Qi in two ways: first, Qi may be discharged together with sweat; secondly, Fire often leads to hyperactivity of the body which then must be supported by more Qi. For these reasons, Syndromes due to pathogenic Fire are not only manifested by Heat symptoms, but also manifested by symptoms of Deficiency of both Yin Fluids and Qi, such as thirst with preference for Cold drinks, dry throat and tongue, scanty and dark urine, constipation, and lassitude.
Third , fire tends to accelerate circulation of Blood and to cause Internal Wind. The Heart belongs to Fire in the Five Elements and controls Blood vessels, so pathogenic Fire has an affinity for Blood and tends to enter the Blood vessels to cause the accelerated flow of Blood or even bleeding. Clinically, this is marked by various kinds of bleeding such as hematemesis, epistaxis, uremia, hemafecia, and metrorrhagia. Also Fire tends to consume Yin Fluids and to lead to malnourishment of the tendons, giving rise to convulsion, upward staring of the eyes, a stiff neck or opisthotonos, the symptoms of internal Wind.
Fourth, fire is responsible for skin ulcers and swelling. Fire entering the Blood vessels may collect in certain areas, leading to abscesses or skin ulcers. This is why such diseases are manifested as redness, swelling, heat and pain in the affected part.
often disturbs Heart Spirit. According to the Five Elements theory, Fire
is closely related to the Heart, which controls the spirit. So disturbance
of Heart Spirit is often present in the case of pathogenic Fire attacking
the body, manifested as dys- phoria, insomnia, mania, coma, delirium,
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