Yin and Yang are the fundamental principles of the Eight Principles differentiation in Traditional Chinese Medicine (TCM). In diagnosis, diseases can be classified into two main aspects based on the pathological nature of clinical symptoms: Yin and Yang. Yin and Yang can summarize the contents of the other six aspects of the Eight Principles differentiation, namely, exterior, heat, and excess belong to Yang; interior, cold, and deficiency belong to Yin. Therefore, some refer to the Eight Principles as “two principles and six essentials.” In clinical practice, Yin and Yang syndromes are sometimes not distinctly separable, often presenting complex symptoms where Yin contains Yang and Yang contains Yin, such as simultaneous exterior and interior diseases, mixed cold and heat, and mixed deficiency and excess syndromes.
(1) Yin Syndrome Any syndrome that conforms to the general attributes of “Yin” is termed Yin syndrome. For example, interior syndrome, cold syndrome, and deficiency syndrome generally fall under the category of Yin syndrome.Clinical Manifestations: Generally, interior deficiency cold syndrome is classified as Yin syndrome. Patients may exhibit a tendency to lie quietly against a wall, close their eyes, dislike light (preferring darkness and drowsiness, avoiding social interaction), curl up, feel heavy, have a pale or dull complexion, experience fatigue and weakness, shallow breathing, be quiet and speak little, have a low and timid voice, show mental lethargy, and may appear confused or in a stupor. They may grasp at empty air, feel around for clothing or the bed, prefer warmth, have a pale and dry mouth with no thirst, feel cold, have cold hands and feet, dry skin, clear and prolonged urination, loose stools, a deep and slow or weak and thin pulse, a pale and swollen tongue with a white and moist coating. Additionally, any disease affecting the blood or internal organs also falls within the scope of Yin syndrome.Symptom Analysis: Mental lethargy, fatigue, and a low voice are manifestations of deficiency syndrome. Cold limbs, clear and prolonged urination, and loose stools indicate interior cold. A pale and swollen tongue, deep and slow pulse, weak, thin, and rough pulse are all signs of deficiency cold.
(2) Yang Syndrome Any syndrome that conforms to the general attributes of “Yang” is termed Yang syndrome. For example, exterior syndrome, heat syndrome, and excess syndrome generally fall under the category of Yang syndrome.
Clinical Manifestations: Generally, exterior heat excess syndrome is classified as Yang syndrome. Patients with Yang syndrome may lie facing outward, open their eyes and enjoy seeing people (with some exceptions for light sensitivity), stretch out their limbs, feel light, have a red complexion, flushed face, bright eyes, experience chills and fever, have hot skin, dry mouth and throat, desire cold drinks, feel irritable and unable to sleep, be restless, speak incoherently, have a coarse or loud voice, exhibit deep and rapid breathing, wheezing with phlegm, have a clear and loud voice, feel hot with warm hands and feet, have moist skin, experience constipation with foul-smelling stools, and have painful and short urination. Their pulse may be floating, rapid, or strong and forceful, and their tongue may be red with a yellow, thick, dry, or black coating. Additionally, any disease affecting the Qi aspect (or Wei aspect) or the bowels also falls within the scope of Yang syndrome.Symptom Analysis: Yang syndrome encompasses exterior syndrome, heat syndrome, and excess syndrome. The presence of chills and fever indicates the characteristics of exterior syndrome. A red complexion, irritability, hot skin, and dry mouth with a desire for cold drinks are manifestations of heat syndrome. A coarse voice, deep breathing, wheezing with phlegm, and constipation are also signs of excess syndrome. A red tongue with a yellow or black coating and a rapid, strong pulse are indicative of excess heat.
(3) Differentiation between Yin and Yang SyndromesYin Syndrome Yang SyndromeObservation: Pale or dull complexion, heavy body curled up, fatigue and weakness, lethargy, pale and swollen tongue with a moist coating. Flushed or bright complexion, prefers coolness, restlessness, dry and cracked lips, red tongue, yellow or dark yellow coating, possibly cracked or black with prickles.Listening: Low voice, quiet and speaking little, weak and short breaths. Loud voice, irritable and talkative, coarse breathing, wheezing with phlegm, incoherent speech.Inquiry: Foul-smelling stools, reduced appetite, no thirst or preference for hot drinks, clear and prolonged urination. Stools may be hard or constipated, foul-smelling, aversion to food, dry mouth, thirst, short and painful urination.Pulse: Abdominal pain relieved by pressure, cold body with cold feet, deep and weak or thin and rough pulse, weak and slow. Abdominal pain aggravated by pressure, hot body with warm feet, floating, rapid, strong, and forceful pulse.Yin and Yang are relative; when Yang is strong, Yin is weak, and when Yin is strong, Yang is weak. For example, if the pulse is strong and large, the tongue is red and dry, and there is thirst and fever, it indicates Yang excess and Yin deficiency. Conversely, if the pulse is deep and slow, the tongue is pale and moist, and there is abdominal pain and diarrhea, it indicates Yin excess and Yang deficiency. Furthermore, the complex changes of Yin and Yang manifest specifically in the six principles of exterior and interior, cold and heat, deficiency and excess.Yin deficiency syndrome is also known as deficiency heat syndrome, while Yang deficiency syndrome is also known as deficiency cold syndrome. The kidneys are the root of Yin and Yang in the body. When Yin and Yang are deficient for a long time, or due to prolonged illness, it can damage kidney Yin and Yang, leading to kidney Yin deficiency or kidney Yang deficiency, which is termed true Yin deficiency or true Yang deficiency.According to Gu Songyuan’s Medical Mirror, the differentiation of Yin and Yang diseases can also be referenced by the severity of symptoms during day and night. For instance, “Yang diseases are more severe during the day and lighter at night, as Yang Qi and pathogenic Qi are both strong; Yin diseases are lighter during the day and more severe at night, as Yin Qi and pathogenic Qi are both strong. If Yang deficiency occurs, it is lighter during the day; if Yin deficiency occurs, it is lighter at night, with Yin and Yang each returning to their respective states. This also indicates their changes, and should not be rigidly adhered to. This emphasizes that the treatment should be determined by the timing of the disease; if it is not yet manifested, one should welcome and guard against it (following the principle of treating Yin and Yang accordingly). If it is in the acute phase, one should avoid its sharp edge; if it has already caused harm, one should counteract its lethargy. Whether it is day or night, the timing of treatment should not be rigidly adhered to, as it is purely a deficiency syndrome, and one should take nourishing herbs to support the body’s righteousness.
(4) True Yin Deficiency (Kidney Yin Deficiency)True Yin deficiency is caused by the deficiency of true Yin in the kidneys, often seen clinically due to chronic consumptive diseases such as pulmonary tuberculosis.Clinical Manifestations: Symptoms of deficiency heat include a pale face with red cheeks, lips resembling being painted red, five hearts feeling hot, dizziness, tinnitus, dry mouth and throat, hot palms and soles, dizziness, weak lower back and knees, night sweats, nightmares, constipation, short and scanty urination, a thin and rapid pulse, and a red, dry tongue with little coating.Symptom Analysis: Prolonged illness damages Yin essence, affecting true Yin, leading to Yang not being restrained by Yin, resulting in the rise of deficiency heat. This is why one may see a pale face with red cheeks, red lips, dry mouth, five hearts feeling hot, night sweats, constipation, scanty urination, a red, dry tongue, and a thin, rapid pulse. Additionally, since the disease has affected kidney Yin, symptoms of kidney dysfunction may appear, such as dizziness, blurred vision, weakness in the lower back and legs, and night sweats. The kidney governs marrow and bones, so dysfunction may lead to symptoms like tinnitus resembling cicadas, and since the kidney governs reproduction, internal heat may disturb the essence, leading to nocturnal emissions.
(5) True Yang Deficiency (Kidney Yang Deficiency)True Yang deficiency is due to insufficient true Yang in the kidneys, leading to Yang not supporting Yin, often seen in various diseases associated with declining bodily functions and reduced basal metabolism, especially in the elderly or weak individuals.Clinical Manifestations: Symptoms include a pale complexion, cold limbs, fatigue and a tendency to lie down, cough with swelling, pale lips and tongue, a bland mouth with excessive saliva, cough with swelling, spontaneous sweating, dizziness, lack of appetite, abdominal distension, swelling of the lower limbs, loose stools or early morning diarrhea, poor digestion, impotence, nocturnal emissions, premature ejaculation, cold uterus leading to infertility, a pale, moist or swollen tongue, a white, slippery coating, and a deep, slow or weak pulse.Symptom Analysis: Prolonged illness damages Yang Qi, affecting true Yang, leading to Yin cold prevailing internally, resulting in Yang deficiency symptoms. This is why one may see a pale complexion, cold limbs, pale lips and tongue, a bland mouth with excessive saliva, spontaneous sweating, lack of appetite, a pale, swollen tongue, a white, slippery coating, and a deep, weak pulse. Additionally, since the disease has affected kidney Yang, symptoms of kidney dysfunction may appear, such as difficulty in breathing and water retention, abdominal distension, and swelling of the lower limbs. Dysfunction in reproductive functions may lead to impotence, premature ejaculation, and infertility; Yang deficiency may also lead to early morning diarrhea.
(6) Loss of Yin Loss of Yin refers to the syndrome characterized by a significant loss of body fluids, leading to symptoms of Yin fluid depletion. Loss of Yin is a type of deficiency heat syndrome.Clinical Manifestations: Symptoms include profuse sweating, shortness of breath, feeling hot, warm hands and feet, restlessness or confusion, dry mouth and throat, dry and cracked lips and tongue, wrinkled skin, sunken eyes, dry and cracked lips and tongue, scanty or absent urination, a preference for cold drinks, a red and dry tongue, and a thin, rapid pulse. Typically, profuse sweating is a characteristic of loss of Yin, with the sweat being warm, salty, and thin (loss of Yin due to vomiting or diarrhea may not always present with profuse sweating).Symptom Analysis: The depletion of Yin fluids results in the loss of their moistening function, leading to dry mouth and throat, dry and cracked lips and tongue, and wrinkled skin. The depletion of fluids leads to scanty urination. Deficiency of Yin leads to internal heat, resulting in a warm body and warm limbs. If deficiency heat rises, it leads to restlessness. A red and dry tongue, along with a thin, rapid pulse, indicates signs of Yin depletion and deficiency heat. Profuse sweating often occurs in patients with a history of heat diseases, where the heat pathogen forces the sweat to leak out. It can also occur in patients who have been treated improperly and have excessive sweating. At this time, profuse sweating is both a cause and a symptom of loss of Yin.
(7) Loss of Yang Loss of Yang refers to a syndrome characterized by Yang deficiency leading to cold symptoms. The body’s functional activity is low.Clinical Manifestations: Symptoms include profuse sweating, a pale complexion, mental lethargy, cold limbs, a tendency to curl up, a preference for warm drinks, bland taste, weak breath, a pale, moist tongue, and a weak or floating pulse.Symptom Analysis: Loss of Yang occurs in various conditions leading to Yang Qi deficiency, resulting in a loss of function. Yang deficiency cannot restrain, leading to excessive sweating, which is a characteristic of loss of Yang. Yang deficiency leads to cold, resulting in a cold body and cold limbs.
(8) Differentiation between Loss of Yin and Loss of Yang Loss of Yin and Loss of Yang are dangerous syndromes of diseases. If differentiation is incorrect or treatment is delayed, death may occur immediately. Loss of Yin and Loss of Yang refer to the rapid loss of the material basis of life activities and the decline of functional capacity. Both Loss of Yin and Loss of Yang are caused by high fever, profuse sweating, severe vomiting and diarrhea, excessive blood loss, severe dehydration, collapse, shock, or treatment errors. Loss of Yin and Loss of Yang are two different types of syndromes. The fundamental cause of Loss of Yin is the significant loss of body fluids, leading to Yin depletion. The main cause of Loss of Yang is the loss of Yang Qi. Since Qi can be lost with fluids and blood, Loss of Yang is often seen after excessive sweating, vomiting, diarrhea, or severe bleeding. Many critical stages of diseases may also present with Loss of Yang. Yin and Yang are opposites and interdependent; when Yin is depleted, Yang Qi will have no support and will disperse. When Yang is lost, Yin fluids will have no transformation and will be exhausted. Therefore, Loss of Yin can quickly lead to Loss of Yang, and Loss of Yang often follows Loss of Yin. The two are only different in priority and sequence, with no clear boundary. In clinical practice, it is essential to differentiate the priority of Loss of Yin and Loss of Yang and provide timely treatment.Loss of Yin Syndrome Loss of Yang SyndromeSweat: Warm, salty, not sticky. Sweat: Cool, bland, slightly sticky.Limbs: Warm. Limbs: Cold.Tongue: Red and dry. Tongue: Pale and moist.Pulse: Thin and rapid. Pulse: Weak and faint.Other: Body heat, restlessness, thirst, preference for cold drinks. Other: Cold body, curled up, fatigue, bland taste, preference for warm drinks.
(9) Yang Excess Yang excess refers to a pathological state characterized by strong Zheng Qi and excessive pathogenic Qi. Yang excess indicates a pathological state where Zheng Qi has not weakened, Yang Qi is relatively strong, and there is excessive heat. Yang excess often arises from exposure to heat pathogens or other pathogens, leading to Yang transforming into heat; it can also develop from pathological hyperactivity of the body’s functions. Additionally, long-term consumption of spicy, fatty foods or excessive or incorrect use of warming and Yang-tonifying substances can also lead to Yang excess. The main manifestations include strong heat, restlessness, loud voice, red complexion, thirst, dry stools, short and red urination, a rapid and strong pulse, and a red tongue with a yellow coating.
(10) Yin Excess Habitually referred to as Yin predominance or Yin excess, it refers to a pathological state characterized by strong Zheng Qi and excessive Yin Qi, with functional impairment or imbalance and insufficient heat. Yin excess indicates a pathological state where Zheng Qi has not weakened, Yin Qi is relatively strong, and there is insufficient heat. Yin excess often arises from external cold pathogens, excessive consumption of cold foods, or dysfunction or imbalance of internal organs, leading to excessive Yin Qi and suppression of Yang Qi. The main manifestations include cold limbs, aversion to cold, abdominal pain, diarrhea, water retention, curled up with little movement, bland taste, no thirst, clear and thin phlegm, pale tongue with a white coating, and a slow pulse.
(11) Yang Deficiency Yang deficiency refers to the deficiency of Yang Qi, leading to reduced function and insufficient heat, manifesting as a pathological state of deficiency cold. “Yang deficiency leads to external cold” refers to this condition. Yang deficiency often arises from congenital insufficiency, lack of nourishment, overwork, or excessive use of cold-clearing and Yang-reducing medications. Clinical manifestations include a pale complexion, cold limbs, easy sweating, loose stools, clear urination, pale lips, bland taste, pale tongue, white coating, and weak pulse.
Additionally, TCM mentions “Yin Collapse.” Collapse refers to cold limbs that are not warm. Internal organs are deficient and cold, and Yang Qi cannot reach the limbs, resulting in coldness, which is termed Yin Collapse. Yin Collapse actually refers to a more severe Yang deficiency, particularly in the hands and feet.
(12) Yin Deficiency Yin deficiency refers to the deficiency of Yin fluids and their functional decline, leading to a pathological state of deficiency heat, termed “Yin deficiency leads to internal heat.” Yin deficiency often arises from heat pathogens damaging Yin, excessive emotional stress leading to heat damaging Yin, prolonged illness depleting Yin fluids, and insufficient nourishment over time. Clinical manifestations include “five hearts feeling hot,” afternoon tidal fever, night sweats, red lips and dry mouth, tender red or crimson tongue with no coating, constipation, and yellow and scanty urination, with a thin and rapid pulse.
(13) Yang Excess with Yin Deficiency In clinical practice, Yang excess, Yin excess, Yang deficiency, and Yin deficiency often do not exist in isolation. Since Yin and Yang are interdependent, if one side is excessively strong, it will inevitably affect the other side, leading to varying degrees of damage. Yang excess can harm Yin, and Yin excess can harm Yang. The “Su Wen: Discussion on Yin and Yang” states, “If Yin prevails, Yang will be ill; if Yang prevails, Yin will be ill,” referring to this situation.
In a state of Yang excess, the intense Yang Qi will inevitably cause varying degrees of damage to Yin fluids. When the damage is light and symptoms are not obvious, the essence of the disease remains Yang excess; when the damage is severe and symptoms are apparent, such as dry mouth, feeling hot, scanty and red urination, dry stools, and dry skin, it transforms into Yang excess with Yin deficiency, where the essence of the disease is a combination of excess and deficiency.
(14) Yin Deficiency with Yang Excess Habitually referred to as Yin deficiency with Yang hyperactivity, Yang hyperactivity is synonymous with Yang excess. To standardize the diagnostic terminology, we will refer to Yang hyperactivity as Yang excess. Yin deficiency with Yang excess and Yang excess with Yin deficiency are two syndromes with similar clinical manifestations but different pathogenesis. Yang excess with Yin deficiency arises from Yang excess, which subsequently depletes Yin fluids; Yin deficiency with Yang excess arises from the deficiency of essence or fluids, leading to Yang Qi losing its restraint over Yin fluids, resulting in hyperactivity and the manifestation of Yang excess. Yin deficiency can lead to Yang hyperactivity, while Yang excess can deplete Yin fluids, exacerbating Yin deficiency, creating a reciprocal relationship. Clinical manifestations include tidal fever, night sweats, five hearts feeling hot, coughing blood, weight loss, insomnia, irritability, or nocturnal emissions, increased sexual desire, a red and dry tongue, and a thin and rapid pulse.
Additionally, there is Yin deficiency with Yang floating, which refers to the pathological change of true Yin deficiency and loss of fluids leading to Yang Qi floating upwards. The main manifestations include dizziness, flushed face, red eyes, dry throat, sore throat, and toothache. Yin deficiency with Yang floating is similar to Yin deficiency with Yang excess, but the symptoms are concentrated in the upper body.
(15) Yin Excess with Yang Deficiency When Yin fluids are excessively strong, they will inevitably cause varying degrees of damage to Yang Qi. When Yang damage is light and symptoms are not obvious, the essence of the disease remains Yin excess with cold; when Yang damage is severe and symptoms are apparent, it manifests as aversion to cold, pale complexion, clear and prolonged urination, and loose stools, indicating Yang deficiency and the essence of the disease transforms into Yin excess with Yang deficiency, primarily characterized by cold with accompanying Yang damage.
(16) Both Yin and Yang Deficiency Both Yin and Yang deficiency result from mutual damage. When either Yin fluids or Yang Qi are deficient to a certain extent, it will affect the other, leading to the pathological changes of both Yin and Yang deficiency. Mutual damage occurs on the basis of either Yin deficiency or Yang deficiency, further developing into both Yin and Yang deficiency. Since the kidneys are the “home of water and fire,” housing the original Yin and Yang, they are the foundation of Yin and Yang for all organs. Therefore, any deficiency of Yin or Yang in any organ will inevitably affect kidney Yin or Yang; when kidney Yin or Yang is deficient to a certain extent, it will also affect the other, resulting in both Yin and Yang deficiency. Clinically, both Yin and Yang deficiency can present in two situations: One is the predominance of Yang deficiency in both Yin and Yang deficiency, which arises from more severe Yang Qi deficiency affecting Yin fluids, leading to insufficiency. The main characteristics are: simultaneous presence of deficiency cold and deficiency heat, with deficiency cold being predominant and deficiency heat being secondary. The other is the predominance of Yin deficiency in both Yin and Yang deficiency, which arises from more severe Yin fluid deficiency affecting Yang Qi, leading to insufficiency. The characteristics are: simultaneous presence of deficiency cold and deficiency heat, with deficiency heat being predominant and deficiency cold being secondary.
(17) Separation of Yin and Yang Separation of Yin and Yang, also known as Yin depletion and Yang collapse, refers to a severe stage of disease where Yin and Yang can no longer support each other, leading to a pathological phenomenon of disintegration. When clinical symptoms of significant blood loss, severe vomiting and diarrhea, high fever, and other severe loss of Yin symptoms appear, Yin fluids have already been depleted, and Yang Qi may collapse at any time; internal injuries from various diseases, such as heart Yin deficiency, may also lead to Yang Qi collapse. Separation of Yin and Yang is the most severe imbalance of Yin and Yang and is a critical mechanism of life-threatening conditions and death.
Additionally, it is important to note that in traditional TCM theory, the frequently discussed Yin and Yang syndromes. In the previous section, we mentioned that it is impossible to use Yin and Yang syndromes to encompass all diseases. The specific meanings of Yin and Yang syndromes refer to deficiency cold syndrome and excess heat syndrome. Combining the differentiation of Yin and Yang with the significance of disease location, it can be accurately stated that Yin syndrome refers to Yang deficiency with cold, while Yang syndrome refers to excess Yang with heat.
Importance of Differentiating Yin and Yang
The six meridians derive from the Eight Principles. The essence of the six meridians consists of three disease locations and two disease natures, with the two disease natures being Yin and Yang. From the perspective of disease nature, all diseases in the world are either Yin syndromes or Yang syndromes. Therefore, the “Su Wen: Discussion on Yin and Yang” states: “Yin and Yang are the principles of heaven and earth, the framework of all things…” Zhang Jingyue in the “Complete Works of Jingyue: Transmission of Loyalty” pointed out: “Yin and Yang are the guiding principles of medicine; in diagnosing and treating diseases, one must first examine Yin and Yang.”
Yin and Yang are very important, including the first course in TCM colleges, “Fundamentals of TCM Theory,” which also begins with Yin and Yang. “TCM Diagnosis” also discusses differentiating Yin and Yang. But do we have a clear understanding of differentiating Yin and Yang in our minds? How do we differentiate Yin and Yang in clinical practice?
The essence of Yin and Yang is cold and heat, deficiency and excess; excess and heat belong to Yang syndrome, while deficiency and cold belong to Yin syndrome. Yin and Yang are relatively abstract, while cold and heat, deficiency and excess are more concrete. Therefore, the differentiation of Yin and Yang in clinical practice relies on differentiating cold and heat, deficiency and excess. As long as we can clearly distinguish cold and heat, deficiency and excess, we can clarify Yin and Yang. The “Complete Works of Jingyue: Transmission of Loyalty” also states: “The six changes are exterior, interior, cold, heat, deficiency, and excess; these are the keys in medicine. By clarifying these six, all diseases can be addressed… By clarifying these six changes and understanding Yin and Yang, the diseases of the world cannot escape these eight categories.” This emphasizes the importance of distinguishing cold and heat, deficiency and excess.
Since Yin syndromes are often deficient and cold, while Yang syndromes are often excess and hot, we can completely achieve the goal of differentiating Yin and Yang by distinguishing cold and heat, deficiency and excess. In our previous discussion of the “Six Steps of Differentiating and Treating Classical Formulas,” we mentioned that as long as we clarify cold and heat, deficiency and excess, Yin and Yang will be clear. However, is it more important to distinguish cold and heat or deficiency and excess? We often use Zhang Fei and Lin Daiyu as representatives of Yang syndrome and Yin syndrome, respectively. What is the fundamental difference between Zhang Fei and Lin Daiyu?
Zhang Fei is tall and strong, with a powerful voice, and his pulse is long and strong, so he is a case of excess syndrome, Yang syndrome. Lin Daiyu is delicate and weak, with a frail body, and her pulse is weak and feeble, making her a case of deficiency syndrome, Yin syndrome. If Zhang Fei and Lin Daiyu both go out in the rain and catch a cold, the external pathogen is the same, but the difference lies in their Zheng Qi. Zhang Fei’s Zheng Qi is relatively sufficient, so the struggle between Zheng and pathogenic Qi is strong, indicating a Yang syndrome. In the exterior, it is a Taiyang disease; in the interior, it is a Yangming disease. Lin Daiyu’s Zheng Qi is insufficient, making her unable to resist the pathogen, indicating a Yin syndrome. In the exterior, it is a Shaoyin disease; in the interior, it is a Taiyin disease, and the treatment method needs to support Zheng Qi and expel the pathogen. This is their difference.
It is like one country A invading another country B. Country B must rise to resist; the war first occurs at the border. If country B is strong, the war will be intense (the struggle between Zheng and pathogenic Qi is strong), and the war at the border (exterior syndrome) will last for a while. If country B is weak, the enemy will quickly break through the defense line (Zheng Qi is weak and unable to resist the pathogen), leading to the invasion of the interior, similar to the pathogen entering the interior.
Deficiency syndrome and excess syndrome emphasize the deficiency or excess of Zheng Qi. When Zheng Qi is deficient, it is unable to resist the pathogen, indicating a deficiency syndrome that requires supporting Zheng Qi and expelling the pathogen. When Zheng Qi is sufficient, the struggle between Zheng and pathogenic Qi is strong, indicating an excess syndrome that does not require supporting Zheng Qi, but solely expelling the pathogen. Therefore, the deficiency or excess of Zheng Qi determines whether it is a deficiency syndrome or an excess syndrome.
In deficiency syndrome, Zheng Qi is insufficient and unable to resist the pathogen, leading to symptoms reflecting the body’s functional decline. This is manifested as cold syndrome with a preference for warmth, such as Lin Daiyu’s constitution, where Qi and blood are insufficient, and Yang Qi is deficient and unable to warm, leading to a preference for warmth and thicker clothing than usual. In excess syndrome, Zheng Qi is sufficient, and the struggle between Zheng and pathogenic Qi is strong, leading to symptoms reflecting the body’s functional hyperactivity. This is manifested as heat syndrome with a preference for heat, such as Zhang Fei’s constitution, where Zheng Qi is strong, and Yang Qi is sufficient, leading to a dislike of cold and a preference for a cooler environment, often becoming irritable and preferring cold drinks.
Cold syndrome does not arise from the invasion of cold pathogens, but rather from Zheng Qi deficiency; heat syndrome does not arise from the invasion of heat pathogens, but rather from sufficient Zheng Qi. Deficiency syndrome leads to cold syndrome, while deficiency syndrome and cold syndrome lead to Yin syndrome; excess syndrome leads to heat syndrome, while excess syndrome and heat syndrome lead to Yang syndrome. Thus, deficiency and excess determine cold and heat, and deficiency and excess are more important than cold and heat. Therefore, the fundamental difference between Zhang Fei and Lin Daiyu is that the former represents an excess syndrome (sufficient Zheng Qi), while the latter represents a deficiency syndrome (deficient Zheng Qi), determining that the former is a Yang syndrome and the latter is a Yin syndrome.
Five Key Points for Differentiating Yin and Yang
The Yang-supporting school emphasizes warming Yang and skillfully uses ginger, cinnamon, and Aconite. The core knowledge of the Yang-supporting school is to differentiate Yin and Yang, and it provides the most detailed discussion on differentiating Yin and Yang syndromes. Therefore, based on the understanding of the Yang-supporting school, we propose five key points for differentiating Yin and Yang, which are also diagnostic criteria for differentiating Yin and Yang syndromes.
Zheng Qinan states:
In Yang deficiency disease, the person must have a pale complexion, blue-white lips, lack of spirit, closed eyes, low voice, shortness of breath, little energy, heavy body, aversion to cold, clear saliva, lack of appetite, and a tongue that is blue and slippery, or black and moist, or pale yellow and moist, with excessive saliva, not thirsty for water, even if offered, prefers hot soup, and has frequent urination. The pulse is floating and weak, with cold limbs, and abdominal pain that is relieved by pressure. All these symptoms are the true face of Yang deficiency, and the treatment should focus on supporting Yang and suppressing Yin.
In Yin deficiency disease, the person must have a red complexion, energetic spirit, open eyes, loud voice, foul breath, light body, aversion to heat, unproductive urination, thirst for cold drinks, a dry yellow or black tongue, and a complete lack of fluids, with prickles in the mouth, irritability, delirium, or tidal fever and night sweats, dry cough without phlegm, and excessive thirst. The pulse is long and strong, and all these symptoms are the true face of Yin deficiency, and the treatment should focus on nourishing Yin to break Yang.
The above two paragraphs describe the differentiation between Yin and Yang syndromes comprehensively. Yang deficiency disease is Yin syndrome, while Yin deficiency disease is Yang syndrome. To make it more intuitive, we have summarized the following table, mainly focusing on observation, thirst, urination, tongue diagnosis, and pulse diagnosis to comprehensively determine Yin and Yang syndromes.
