1. Wind
(1) Natural Characteristics: Wind has the properties of lightness, dispersion, and movement, making it the primary qi of spring. Among the twenty-four solar terms, the four terms of Major Cold, Beginning of Spring, Rain Water, and Awakening of Insects are dominated by wind qi. Since wind is associated with wood qi and connects to the liver, spring is also referred to as the season of wind and wood. Although wind is the primary qi of spring, it is present throughout the year and can occur in all seasons. Therefore, diseases caused by wind are more common in spring but can also occur in other seasons.
(2) Nature and Pathogenic Characteristics of Wind Evil: The basic characteristics of wind are its lightness, variability, and ability to cause movement. When wind is excessive, it leads to movement, making it the leader of all diseases.
① Lightness and Dispersion: Wind is a yang evil, characterized by lightness and upward dispersion. Therefore, when wind causes disease, it tends to harm the upper body and can easily invade the skin and waist, which are yang areas. The lungs, being the ‘canopy’ of the five organs, when harmed by wind, lead to symptoms such as nasal congestion, runny nose, throat itch, and cough. When wind disturbs the head and face, symptoms like dizziness, headaches, neck stiffness, facial paralysis, and crooked mouth can occur. Wind evil invading the skin can lead to symptoms like aversion to wind and fever. Due to its dispersive nature, wind evil can invade the skin, causing the pores to open and resulting in sweating and aversion to wind.
② Variability: Wind is characterized by its ability to move and change unpredictably. This means that diseases caused by wind can shift locations and are often unpredictable. For example, wind rashes and urticaria can appear and disappear without warning; wandering pain in the limbs and joints, known as wind bi (wind obstruction), is also a manifestation of excessive wind qi. The variability of wind evil is evident in conditions like epilepsy and sudden fainting due to stroke. In summary, diseases led by wind, whether caused by external factors or internal injuries, generally exhibit rapid onset, frequent changes, and quick transmission.
③ Active Nature of Wind: The active nature of wind refers to its characteristic of being unstable and causing movement. This is often manifested as dizziness, tremors, limb spasms, and other symptoms, hence the saying “when wind is excessive, movement occurs.” For instance, in external heat diseases, the phrase “extreme heat generates wind” or in internal injuries, conditions like “liver yang transforming into wind” or “blood deficiency generating wind” all exhibit the active nature of wind evil.
④ Wind as the Leader of All Diseases: Wind evil is the leading cause of external diseases, with cold, dampness, dryness, and heat often accompanying it. For example, when combined with cold, it becomes wind-cold evil; with heat, it becomes wind-heat evil; with dampness, it becomes wind-damp evil; with summer heat, it becomes summer wind; with dryness, it becomes wind-dryness; and with fire, it becomes wind-fire. Therefore, clinically, wind evil is frequently encountered and easily combines with the six excesses to cause disease. Hence, wind is referred to as the leader of all diseases and the foremost among the six excesses.
Wind corresponds to the liver. Wind is associated with wood qi and connects to the liver. External wind evil can lead to symptoms like stomach pain, abdominal distension, borborygmus, vomiting, and diarrhea. This is due to wind evil harming the liver, where excessive wood overcomes earth.
In summary, wind is the primary qi of spring and corresponds to the liver wood. Wind evil can cause a wide range of diseases and changes rapidly. Its specific characteristics include: ① It can affect the entire body: Wind can invade any part of the body, from the head to the feet, externally affecting the skin and internally affecting the organs. ② Mediating Role: It can combine with cold, dampness, heat, dryness, and fire to cause disease. ③ Its pathogenic specificity: Wind diseases have rapid onset and short duration, with symptoms that are easy to recognize, such as sweating, aversion to wind, generalized itching, wandering pain, numbness, and instability. In clinical practice, if the onset occurs in spring and is clearly related to wind evil, the presence of wind evil should be considered.
2. Cold
(1) Natural Characteristics: Cold has the properties of coldness and condensation, making it the primary qi of winter. The four solar terms of Minor Snow, Major Snow, Winter Solstice, and Minor Cold are dominated by cold qi. Cold is associated with water qi and connects to the kidneys, hence winter is referred to as the season of cold water. Due to winter being the season of cold qi, cold diseases are more common in winter but can also occur in other seasons. Sudden drops in temperature and inadequate protection against the cold can make the body susceptible to cold evil.
(2) Nature and Pathogenic Characteristics of Cold Evil: Cold evil is characterized by coldness, stagnation, and contraction.
① Cold Easily Harms Yang: Cold is a manifestation of yin qi, thus it is a yin evil. Yang qi can normally control yin, but when yin cold is excessive, yang qi is not only insufficient to dispel cold evil but is also harmed by it. Hence, it is said that “when yin is excessive, cold prevails” and “when yin is excessive, yang diseases occur.” Therefore, cold evil is most likely to damage the body’s yang qi. When yang qi is damaged, it loses its warming function, leading to obvious cold symptoms in the whole body or locally. For instance, when cold evil constricts the exterior, it obstructs the defensive yang, resulting in symptoms like aversion to cold, fever, and absence of sweating, known as “cold damage.” If cold evil penetrates internally and harms the yang qi of the organs, it is referred to as “internal cold.” For example, if it harms the spleen and stomach, it can lead to abnormal digestion and absorption, resulting in vomiting, diarrhea, and abdominal pain; if it affects the lungs and spleen, it can lead to cough and shortness of breath with clear phlegm or edema; if cold harms the spleen and kidneys, it can lead to cold limbs, lower back pain, clear urination, and abdominal swelling; if there is heart and kidney yang deficiency, cold evil can penetrate the lesser yin, leading to symptoms like aversion to cold, curled up posture, cold extremities, diarrhea with clear stools, mental fatigue, and thin pulse.
② Cold Nature of Stagnation: Stagnation refers to the obstruction and blockage caused by cold. The movement of qi, blood, and body fluids in the human body relies on the warming function of yang qi to be smooth and unobstructed. When cold evil invades the body, the meridians and blood are deprived of the warmth of yang qi, leading to stagnation and blockage, which causes pain. Pain caused by cold is alleviated by warmth and worsens with cold; warmth promotes the flow of qi and blood, alleviating or reducing pain. Cold predominates in pain, but pain does not necessarily mean cold. Due to the different locations of cold invasion, the symptoms can vary. If cold invades the skin, it can cause severe pain in the head, body, and limbs; if cold evil penetrates internally, it can cause cold pain or cramping in the chest, abdomen, or other areas.
③ Cold Nature of Contraction: Contraction refers to the pulling and tightening nature of cold. Cold evil can cause the qi mechanism to contract, leading to blockage of the pores and constriction of the meridians and tendons. If cold invades the meridians and joints, it can cause tightness and pain, leading to difficulty in movement or numbness; if cold evil invades the skin, it can cause the pores to close, leading to fever and aversion to cold without sweating.
Cold corresponds to the kidneys. Cold is associated with water qi and connects to the kidneys. When cold evil invades, it can lead to symptoms like reduced urination and edema due to excessive cold water; excessive cold water can also obstruct heart fire, leading to heart pain, palpitations, and cold extremities.
In summary, cold is the primary qi of winter and corresponds to kidney water. Cold diseases are more common in winter but can also occur in other seasons. The pathogenic characteristics of cold evil include: cold as a yin evil easily harms yang qi, leading to obvious cold symptoms in the body or locally. Cold predominates in pain, making pain one of the important characteristics of cold syndrome. Due to cold, the qi contracts, leading to symptoms like closed pores, retraction of qi, and tightness in the tendons, manifesting as absence of sweating, tightness, and pain or difficulty in movement.
3. Summer Heat
(1) Natural Characteristics: Summer heat is a fire evil and the primary qi of summer. The four solar terms of Minor Fullness, Grain in Ear, Summer Solstice, and Minor Heat are dominated by summer heat. Summer heat has a clear seasonal characteristic, primarily occurring from the Summer Solstice to the Beginning of Autumn. Summer heat is unique to the summer season, hence the saying “summer heat is an external evil, with no internal summer heat.” The pathogenic effects of summer heat can be divided into yin and yang. In the hot summer days, excessively high temperatures, prolonged exposure to the sun, or working in a hot environment can lead to heat diseases, which are classified as yang summer heat; while during the hot season, overconsumption of cold foods, excessive exposure to coolness, or prolonged cold baths can lead to heat diseases classified as yin summer heat. In summary, summer heat in the summer is classified as yin summer heat when exposed to cold and yang summer heat when exposed to heat.
(2) Nature and Pathogenic Characteristics of Summer Heat Evil: Summer heat is transformed from fire, primarily characterized by upward movement and often accompanied by dampness.
① Nature of Summer Heat: Summer heat is characterized by the intense heat of summer, which is a yang evil. The harm caused by summer heat often manifests as a series of yang heat symptoms, such as high fever, irritability, red face, restlessness, and a rapid pulse, known as heat stroke (or summer heat).
② Nature of Upward Movement: Upward movement refers to the tendency of summer heat to invade the head and disturb the heart spirit. Summer heat easily enters the heart and can cause the pores to open, leading to excessive sweating. Excessive sweating can deplete body fluids, resulting in symptoms like thirst, dry lips, and short, red urination. When sweating excessively, qi can also be lost along with the fluids, leading to qi deficiency, which can result in shortness of breath and fatigue, and in severe cases, sudden fainting, known as heat stroke. Heat stroke can also present with cold extremities, referred to as heat syncope. Summer heat can also provoke liver wind, leading to symptoms like limb spasms, neck stiffness, and even opisthotonos, known as summer wind (summer epilepsy). Summer heat not only depletes qi and body fluids but can also disturb the heart spirit, causing irritability and restlessness.
③ Summer Heat Often Accompanied by Dampness: The summer season is not only hot but also often rainy and humid, leading to the combination of heat and dampness. The clinical features of summer heat often include symptoms of dampness, such as fatigue in the limbs, chest tightness, nausea, and loose stools. Although summer heat and dampness coexist, summer heat is the primary concern, while dampness is secondary; it is not necessary for summer heat to always be accompanied by dampness. Summer is the primary qi of summer, and summer heat can be classified into yin summer heat and yang summer heat. The basic characteristics of summer heat evil include intense heat, yin damage, qi depletion, and often accompanied by dampness. Therefore, clinically, summer heat is characterized by intense heat, yin deficiency, qi deficiency, and damp obstruction.
4. Dampness
(1) Natural Characteristics: Dampness has the properties of heaviness, turbidity, stickiness, and downward tendency, making it the primary qi of late summer. The four solar terms of Major Heat, Beginning of Autumn, End of Heat, and White Dew are dominated by damp qi. Dampness corresponds to the spleen earth. During the transition from summer to autumn, the heat and humidity can lead to the most significant dampness, making late summer a time when damp diseases are most prevalent. Dampness can also arise from exposure to water, rain, or damp living conditions. Damp evil can occur in all seasons, and its effects are often slow and difficult to detect.
(2) Nature and Pathogenic Characteristics of Damp Evil: Dampness is a yin evil that obstructs the qi mechanism and easily harms yang qi, characterized by heaviness, turbidity, stickiness, and a downward tendency.
① Dampness as a Yin Evil: Dampness is similar to water, which is yin in nature. Therefore, dampness is a yin evil. When dampness invades the body, it tends to stagnate in the organs and meridians, obstructing the qi mechanism and causing abnormal qi movement. The chest and flanks are pathways for qi movement; dampness obstructing the chest can lead to chest tightness; dampness can hinder the spleen and stomach, causing loss of appetite, abdominal distension, and loose stools. Due to dampness being a yin evil, when yin is excessive, it can lead to yang diseases. The spleen governs the transformation and transportation of water and dampness, and it is an earth element that prefers dryness and dislikes dampness, making it particularly susceptible to damp evil. Therefore, when damp evil invades the body, it often affects the spleen, leading to spleen yang deficiency, stagnation of water and dampness, resulting in diarrhea, edema, and reduced urination. “When dampness prevails, yang is weak,” as dampness is a yin evil that can easily harm the body’s yang qi. To resolve dampness, methods to transform qi, drain dampness, and promote urination should be employed to ensure smooth qi movement and drainage of water, allowing dampness to be expelled through urination, thus restoring yang qi.
② Heaviness and Turbidity of Dampness: Dampness is a heavy and turbid evil. The term “heavy” refers to the quality of being heavy and burdensome. Therefore, when dampness causes disease, the clinical symptoms often exhibit heaviness, such as a heavy head, body fatigue, and heaviness in the limbs. If dampness invades the skin, it can cause a feeling of heaviness and obstruction; if dampness stagnates in the meridians and joints, it can lead to numbness and pain in the skin and joints. The term “turbid” refers to the foul and unclean nature of dampness. Therefore, when dampness is present, it is common to see foul and unclear excretions and secretions. For example, if dampness is present in the upper body, it can lead to facial blemishes; if it stagnates in the large intestine, it can cause diarrhea with mucus and blood; if it descends, it can lead to cloudy urination and excessive vaginal discharge; if dampness invades the skin, it can lead to sores, eczema, and foul pus.
③ Sticky Nature of Dampness: The term “sticky” refers to the viscous nature of dampness. This characteristic is mainly reflected in two aspects: first, the symptoms of damp diseases are often sticky and uncomfortable, such as sticky stools, difficult urination, and viscous secretions; second, the course of the disease is often prolonged due to the sticky nature of dampness, which can lead to slow onset, long duration, and frequent recurrences. For example, damp-heat is an external heat disease caused by damp-heat evil. Due to the specific nature of dampness, it often presents with slow onset, slow transmission, and prolonged duration, making it difficult to resolve quickly. Conditions like eczema and damp bi (damp obstruction) are also difficult to resolve quickly due to dampness.
④ Downward Tendency of Dampness: Dampness tends to move downward, similar to water, which is heavy and turbid. Therefore, dampness has a downward tendency and can easily affect the lower parts of the body. Symptoms of dampness are often seen in the lower body, such as edema, which is more pronounced in the lower limbs. Conditions like vaginal discharge, cloudy urination, diarrhea, and dysentery are often caused by dampness descending. However, dampness can invade the body both internally and externally, affecting all parts of the body, not just the lower parts. The saying “those harmed by dampness are first affected below” from the “Su Wen: Tai Yin Yang Ming Lun” indicates that dampness tends to move downward, easily invading the yin areas, which is one of its characteristics.
Dampness is the primary qi of late summer and corresponds to the spleen earth. Damp evil obstructs the qi mechanism and easily harms yang qi, characterized by heaviness, turbidity, stickiness, and a downward tendency. Therefore, damp evil manifests as obstruction of the body’s qi mechanism, spleen yang deficiency, and stagnation of water and dampness, leading to symptoms like chest tightness, abdominal distension, limb heaviness, nausea, diarrhea, and foul secretions and excretions.
5. Dryness
(1) Natural Characteristics: Dryness has the properties of dryness, contraction, and cleansing, making it the primary qi of autumn. The four solar terms of Autumn Equinox, Cold Dew, Frost Descent, and Beginning of Winter are dominated by dry qi. During autumn, the weather becomes more restrained, the air becomes clear, and moisture is scarce, leading to an increase in dryness diseases. Dryness is transformed from the dry heat of autumn and is considered a yang evil among the yin. Dryness can be classified into warm dryness and cool dryness. Early autumn can still have residual heat from summer, and prolonged sunny weather without rain can lead to warm dryness invading the body. In late autumn, as winter approaches, the cold wind can combine with dryness to invade the body, leading to cool dryness. Dryness corresponds to lung qi.
(2) Nature and Pathogenic Characteristics of Dry Evil: Excessive dryness leads to dryness and easily harms the lungs, which is the basic characteristic of dry evil.
① Dryness Harms Body Fluids: Dryness is the opposite of dampness; when dampness is absent, dryness prevails. Dryness is transformed from the dry and killing qi of autumn, characterized by dryness and depletion. Therefore, dry evil is most likely to harm the body’s fluids, leading to various dry symptoms and signs, such as dry skin, cracked lips, dry throat, dry mouth, and dry stools.
② Dryness Easily Harms the Lungs: The lungs are the ‘canopy’ of the five organs and prefer to be moist and dislike dryness, hence they are considered delicate organs. The lungs govern qi and control respiration, directly connecting with the atmosphere. Dryness often enters through the mouth and nose. Dryness, being the primary qi of autumn, is most likely to harm the lungs. When dryness invades the lungs, it can damage lung fluids, leading to symptoms like dry cough with little phlegm, difficult expectoration, or blood-streaked phlegm, as well as wheezing and chest pain.
In summary, dryness is the primary qi of autumn and corresponds to the lungs. Dryness is characterized by its ability to harm body fluids and the lungs. Whether external or internal dryness, symptoms of dryness can be observed in the mouth, nose, throat, lips, as well as dry skin and hair.
6. Fire (Heat)
(1) Natural Characteristics: Fire has the property of heat and is most prevalent in summer. The four solar terms of Spring Equinox, Qingming, Grain Rain, and Beginning of Summer are dominated by fire qi. Since summer is the season of fire, fire corresponds to heart qi. However, fire does not have the same clear seasonal characteristics as summer heat and is not limited by seasonal climate.
(2) The Relationship Between Warmth, Summer Heat, Fire, and Heat: Warmth, summer heat, fire, and heat have similar basic properties but also have distinctions.
Warmth and Heat: Here, warmth and heat refer to pathogenic evils. Warmth is a gradual increase in heat, while heat is an extreme form of warmth; the two differ only in degree and not in essence, hence they are often referred to together. In the study of warm diseases, the term warm evil refers to all warm and hot pathogenic qi, without regard to differences in degree.
Summer Heat and Fire (Heat): Summer heat is the primary qi of summer and is transformed from fire; thus, summer heat is a heat evil. However, summer heat is unique to summer and is purely an external evil, with no concept of internal summer heat. Fire (heat) as a disease does not have clear seasonal characteristics and can also include high temperatures and heat from burning.
Fire and Heat: Fire is the source of heat, while heat is the nature of fire. Fire and heat are both manifestations of excessive yang, hence they are often referred to together. However, there are still certain distinctions; heat is purely an evil qi, while fire can refer to both the body’s righteous qi, known as “lesser fire,” and the pathogenic evil, known as “excess fire.” Generally speaking, heat often belongs to external pathogens, such as wind-heat, summer heat, and warm heat. In contrast, fire often arises from internal imbalances of the organs, such as heart fire, liver fire, and gallbladder fire.
In terms of warmth, heat, and fire, although they are all one qi, warmth can transform into heat, and heat can generate fire, indicating a certain degree of difference. Warmth is a mild form of heat, heat is an extreme form of warmth, and heat is a gradual form of fire, while fire is the extreme form of heat.
(3) The Meaning of Fire: In traditional Chinese medicine, fire can be classified into physiological and pathological, as well as internal and external fire.
① Physiological Fire: Physiological fire is a type of yang qi necessary for maintaining normal life activities, hidden within the organs, and has a warming and transformative effect. This beneficial yang qi is referred to as “lesser fire,” which belongs to the category of righteous qi.
② Pathological Fire: Pathological fire refers to excessive yang, which depletes the body’s righteous qi. This type of fire is known as “excess fire.” Pathological fire can also be classified into internal and external fire.
External Fire: External fire can arise from exposure to warm and hot evil qi or from the transformation of external evils like wind, cold, summer heat, dampness, and dryness into fire, known as “the five qi transform into fire.” Among the five evils, only summer heat is purely external fire, referred to as summer heat. The other evils, such as wind, cold, dampness, and dryness, are not inherently fire evils; they can transform into fire under certain conditions. First, they must be obstructed for a long time to transform into fire. For example, cold can transform into heat, extreme heat can generate fire, warmth and heat can combine, or dampness can transform into heat, leading to intensified heat. Fire can also arise from dryness. Second, the transformation into fire can vary based on individual constitution; those with excessive yang or deficient yin are more prone to fire. Third, the location of the evil invasion can also affect the transformation into fire. For instance, if the evil invades the yangming dry earth, it is more likely to transform into fire; if cold evil penetrates the spleen, it is also likely to transform into fire. Additionally, the ability of the five evils to transform into fire is related to treatment.
Internal Fire: Internal fire often arises from dysfunction of the organs, leading to imbalances in yin, yang, qi, and blood. Extreme emotional distress can also lead to internal fire, known as “the five emotions transform into fire.”
Traditional Chinese medicine classifies fire into righteous and evil types. Righteous fire refers to lesser fire, which can be further divided into “sovereign fire” and “ministerial fire.” “Sovereign fire” refers to the yang qi of the heart, while “ministerial fire” refers to the yang qi of the liver, kidneys, gallbladder, bladder, pericardium, and sanjiao. Among these, the yang qi of the kidneys is also known as “mingmen fire” or “dragon fire,” while the yang qi of the liver is referred to as “thunder fire.” “Sovereign fire” refers only to righteous qi; if it is excessive, it becomes heart fire; while “ministerial fire” encompasses both righteous and evil aspects, and when excessive, it is referred to as “ministerial fire in disorder.” Both “heart fire in excess” and “ministerial fire in disorder” belong to “excess fire,” which is considered evil qi.
(4) Nature and Pathogenic Characteristics of Fire Evil: Fire evil is characterized by burning, inflammation, depletion of qi and body fluids, and stirring of blood.
① Nature of Burning: Burning refers to the characteristic of fire evil to scorch and burn. Therefore, when fire evil causes disease, the body’s excessive yang qi is the primary pathological mechanism, clinically manifesting as high fever, aversion to heat, and a rapid pulse, which are signs of heat excess. In summary, fire heat as a disease is characterized by significant heat symptoms, such as fever and rapid pulse.
② Nature of Inflammation: Fire is a yang evil, characterized by upward movement. Therefore, fire evil has a clear tendency to cause inflammation, often manifesting in the upper body. For example, when heart fire is excessive, it can lead to symptoms like red and painful tongue tips, oral ulcers, and sores; when liver fire is excessive, it can lead to symptoms like severe headaches and red, swollen eyes; when stomach fire is excessive, it can lead to symptoms like swollen gums and bleeding gums.
③ Depletion of Body Fluids and Qi: Fire evil, when it is internal, can easily deplete body fluids, leading to the loss of body fluids and causing symptoms like thirst, dry mouth, short red urination, and constipation. When fire is too strong, it can lead to a decline in qi, as excessive yang heat can severely damage the body’s righteous qi, leading to a decline in physiological functions. Additionally, qi is generated from water, and water can transform into qi; when fire forces fluids to leak, the deficiency of fluids can also lead to qi deficiency, resulting in symptoms like shortness of breath, fatigue, and weakness. In summary, fire evil can either directly damage the body’s righteous qi or cause qi deficiency due to fluid depletion, ultimately leading to a pathological result of fluid depletion and qi exhaustion.
④ Stirring of Blood: Fire evil can easily provoke internal wind and cause blood to move erratically.
Stirring of Wind: When fire heat invades the body, it often scorches the liver meridian, depleting body fluids and causing the liver wind to move internally, known as “extreme heat generates wind.” The combination of wind and fire leads to urgent symptoms, clinically manifesting as high fever, confusion, limb spasms, neck stiffness, and opisthotonos.
Movement of Blood: Blood coagulates with cold and flows with warmth. Fire heat can scorch the vessels and accelerate blood flow, leading to various bleeding symptoms, such as hemoptysis, epistaxis, hematochezia, hematuria, and skin rashes, as well as excessive menstruation and uterine bleeding. Fire heat can also lead to the formation of sores and abscesses, as fire heat can enter the blood level, accumulate locally, and cause necrosis of flesh and blood, leading to symptoms of redness, swelling, and pain in the affected area.
⑤ Easily Causes Sores and Abscesses: Fire heat can enter the blood level, accumulate locally, and lead to necrosis of flesh and blood, resulting in sores and abscesses. “Sores and abscesses originate from fire poison.” “Fire poison” and “heat poison” are common causes of sores and abscesses, with clinical manifestations characterized by redness, swelling, heat, and pain in the affected area.
⑥ Easily Disturbs the Spirit: Fire corresponds to heart qi, which governs blood vessels and houses the spirit. Therefore, when fire evil harms the body, it is most likely to disturb the spirit, leading to symptoms like irritability, insomnia, agitation, and even confusion and delirium.
In summary, fire can be classified into physiological and pathological fire, with this section focusing on pathological fire, also known as fire evil. Fire evil can be classified into external and internal fire. External fire often arises from external pathogens, while internal fire often arises from internal imbalances. Fire evil is characterized by burning, inflammation, depletion of body fluids and qi, stirring of blood, and the tendency to cause sores and abscesses, as well as disturbing the spirit. Its pathogenic effects are widespread, with rapid onset and the potential to spread quickly. Clinically, it presents with high fever, fluid depletion, qi deficiency, liver wind, bleeding, and abnormal mental states.
