1-3. 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.

1-4. 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.

1-5. 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.

1-6. 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.

Fifth, fire 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, etc.

2. Epidemic Pathogens
This refers to a group of pathogens responsible for infectious diseases. They also bear names such as Li Qi, which means they are strenuous and liable to cause severe diseases, Du Qi, which also means that they often impair the body severely, or Yi Qi, which indicates that they are different from the common External pathogenic factors.

It was in the Ming Dynasty that epidemic pathogens were included in TCM. As infectious diseases spread widely and failed to respond to treatment based on the theory of the Six External Pathogens, the ancients summarized the features of epidemic or infectious diseases, and concluded that these diseases were caused by some external pathogens with features different from the Six External Pathogens. So they put forward the concept of epidemic pathogens to explain the mechanism of infectious or epidemic diseases. The special features of epidemic pathogens are:

First, they are obviously epidemic and infectious. Spreading through the air or by contact and entering the body through the nose and mouth, they may cause epidemic diseases that spread rapidly in the community.

Secorrd, the diseases caused by epidemic pathogens usually have a sudden onset, are relatively severe, and have similar manifestations in different individuals.

Third, epidemic pathogens are mostly Warm Heat in nature, so they tend to cause diseases marked by Yang Excess symptoms.

Fourth, the spread and generation of epidemic pathogens are related to seasonal conditions and abnormal changes of climate, extreme Heat, long term draught, and dew or fog.

Fifth, the pathogens often invade the body by polluted air, food and water supply.

3. Internal impairment by the Seven Emotions
3-1. Concept of the Seven Emotions
Joy, anger, worry, anxiety, sorrow, terror and fright are collectively known as the Seven Emotions, which, under normal conditions, are the physiological responses of the human body to enviropmental stimuli. Therefore, they are not pathogenic factors. However, if the emotional stimuli are too sudden or too strong or last a long time, they will disturb the functional activities of Zang-fu Organs, cause disharmony of Qi in its ascent, descent, entry and exit movements, and eventually result in diseases. They cause internal disorders of the body, so they are also called the Seven Emotional states as pathogens responsible for internal diseases.

In the light of TCM theory, the Seven Emotions are closely related to the Five Zang Organs and the circulation of Qi and Blood. On the one hand, they are dependent upon the functional activities of different Zang-fu Organs for their generation; on the other, they affect the functional states of these organs. Therefore, diseases of Zang-fu Organs may be manifested as abnormal changes of the emotions, and emotional changes in excess, in turn, impair these organs. For exainple, stagnation of Liver Qi often presents as emotional depression or irritability, while excessive anger often stagnates the flow of Liver Qi or induces Liver Qi to rise excessively.

3-2. Characteristics of the Seven Emotions as pathogenic factors
Different fromthe Six External Pathogens,which usually invade the human body by attacking the Exterior of the body first, the Seven Emotions in EXcess often impair the corresponding organs directly, leading to adverse flow of Qi and disharmony of Qi and Blood of Zangfu Organs with the ensuing occurrence of disease.

3-3. Impairing the internal organs
The Seven Emotions often impair the internai organs directly, and first of all, the Heart. Emotion, as one kind of mental activity, is controlled by the Heart. However, each of the Seven Emotions is ascribed to a different Zang-Fu Organ in TCM, because emotions take Essence Qi for their material basis. TCM believes that the Heart is related to joy, the Liver to anger, the Lung to worry and sorrow, the Spleen to anxiety, and the Kidney to both terror and fright. Therefore, excessive joy impairs the Heart; excessive anger impairs the Liver, excessive worry or sorrow impairs the Lung, excessive anxiety impairs the Spleen; and excessive terror or fright impairs the Kidney.

Of course, the correspondence of Zangfu Organs with emotional activities by no means indicates that a specific emotion only impairs its corresponding organ, in fact, as the Heart controls spirit, any emotional change in Excess will impair the Heart. In addition, one emotion may impair several organs, for the disturbance of one organ may cause disorders of other organs closely related to it. For example, emotional depression will cause disharmony between the Liver and Stomach or the Liver and Spleen as a result of the impairment of the Liver and the transverse attack of Liver Qi on the Stomach and Spleen.

Emotions are produced based on the flow of Qi and Blood. As the Heart governs Blood and spirit, the Spleen, situated in the Middle Jiao and serving as the hub of the ascent and descent of Qi, dominates transformation and transportation, and the Liver stores Blood and dominates dispersion and discharging, diseases caused by emotional disorders are mostly manifested as disorders of Qi and Blood of these organs. For example, worry often impairs both the Heart and the Spleen, leading to mental disorders and dysfunction of the Spleen. Injured by emotional depression, Liver Qi will go up excessively and Blood will follow the rise of Liver Qi to go upward, leading to distending pain in the hypochndriac region, sighing, dysmenorrhea, amenorrhea, or abdominal masses.

3-4. Disturbing flow of Qi
When emotional states are abnormal, they will affect the ascent, descent, entry and exit of Qi. This is because emotional activities depend on the free flow of Qi.

Anger induces Qi to flow upward. This indicates that excessive anger can induce Liver Qi to go up excessively and give rise to the subsequent upward adverse flow of Blood. As Liver Qi tends to go up and anger corresponds to the Liver, excessive anger injures the Liver and disturbs the nornial descent and ascent of Liver Qi. In such cases, it is often manifested as a red face and eyes, dizziness and vertigo, distending pain of the head, or even sudden coma or syncope. Sometimes, hematemesis and diarrhea may also be seen as a result of Blood following the adverse Qi to rise excessively or due to Liver Qi attacking the Spleen.

Joy relaxes Qi. This includes two aspects. In normal conditions, joy can promote the flow of Qi and Blood, thus it can relax mental strain. However, excessive Joy may cause Qi to flow too fast to be controlled, so there are such manifestations as poor concentration of the Mind, or even mania.

Sorrow consumes Qi. This means that deep sorrow is likeiy to consume Lung Qi, leading to chest depression and demoralization. Voice is produced by the flow of Lung Qi through the throat, and depends on sufficient Lung Qi for its material basis. In a state of sorrow, one is liable to cry or weep for a long time, so Lung Qi is consumed and lassitude, a depressed feeling in the chest, as well as demoralization occur as a result of deficient Lung Qi failing to perform the functional activities of the Lung.

Anxiety stagnates the flow of Qi. When thinking, one must concentrate and Vital Qi will remain in place to support the thinking. Therefore, excessive lengthy or intense thinking will lead to stagnation of Qi, especially Spleen Qi, which tends to accumulate. Manifestations of such a morbid state include poor appetite, abdominal distention, constipation, etc., due to.the stagnation of Spleen Qi.

Fright causes disturbed flow of Qi. When one is suddenly frightened, his or her circulation of Qi will be disturbed, leading to palpitations, a distressed mind, inability to concentrate the mind, etc. Terror induces Qi to flow downward. The Kidney is related to
terror and also controls defecation and urination. These mainly depend on the controlling effect of Kidney Qi, which is produced by Kidney Essence. Excessive terror often leads to incontinence feces and urine, as well as weakness of the legs, as a result of the impairment of Kidney Qi and Kidney Essence, which in turn fail to control defecation and urination and to nourish the bones.

3-5. Worsening or deterioration of a disease
As emotional changes often exert an unfavorable influence on the functional activities of Zangfu Organs and the flow of Qi and Blood, they may worsen or cause a disease to deteriorate. For example, patients with hypertension, a disease caused by excessive rising of Liver Yang due to Deficiency of both Kidney Yin and Liver Yin, may suffer from sudden coma or syncope, or even paralysis in the case of being stimulated by sudden and violent rage. This is because the Liver is related to anger, and sudden anger will induce further excessive rising of Liver Yang.

Of the etiologic factors TCM has identified, External diseases are usually caused by the Six External Pathogens, and infernal diseases by the Seven Emotionai changes in excess