The Eight Principles of Diagnosis is a fundamental method of diagnosis. It utilizes the eight principles of Yin and Yang, Exterior and Interior, Cold and Heat, Deficiency and Excess to analyze and summarize disease patterns, providing a basis for treatment. The differentiation between Exterior and Interior indicates the depth of the disease; Cold and Heat differentiate the nature of the disease; Deficiency and Excess differentiate the strength of pathogenic factors and the body’s righteous Qi; Yin and Yang encompass the other six principles. Exterior, Heat, and Excess belong to Yang, while Interior, Cold, and Deficiency belong to Yin. The four pairs of contradictions in the Eight Principles are relative, interconnected, and transform into one another. The complex clinical symptoms can all be analyzed and summarized using this fundamental method.
The Eight Principles of Diagnosis is the overarching framework for various diagnostic methods in Traditional Chinese Medicine (TCM).
Diagnosis involves analyzing and identifying the symptoms of diseases, which is the main process and method for understanding and diagnosing diseases. “Differentiation” means to recognize and distinguish, which is essentially analysis. “Pattern” refers to the symptoms, which are the comprehensive manifestations of the disordered relationships between the body and environmental factors, as well as between the organs, meridians, Qi, blood, and body fluids under the influence of pathogenic factors. Therefore, clarifying a specific pattern summarizes the pathological conditions of the disease’s development stage, including the causes, locations, the strength of the struggle between pathogenic and righteous Qi, and the relative states of Yin and Yang.
The process of differentiation is based on theories of organs, meridians, Qi, blood, body fluids, and pathogenic factors, integrating and analyzing the symptoms and signs collected through the four diagnostic methods: observation, listening, inquiry, and palpation, to determine their internal relationships and the relationships between various pathological changes, thereby understanding the disease and making an accurate diagnosis.
Differentiation and treatment are two crucial interrelated and inseparable aspects of TCM’s principles, methods, formulas, and medicines in clinical practice. Differentiation is the understanding of the disease, while treatment involves taking corresponding therapeutic measures and methods based on the identified patterns. Differentiation is the premise and basis for treatment, while treatment is the objective of differentiation and an objective standard for verifying the correctness of the differentiation.
“Symptoms” refer to individual signs, which are recognized similarly in both Western and Chinese medicine, such as headache, fever, cough, palpitations, nausea, etc.
“Disease” refers to the name of the illness. Among the disease names in TCM, only a few correspond to Western medical terms, such as measles, diphtheria, tetanus, asthma, dysentery, and heat stroke, while most terms differ. Due to the differences in theoretical systems, the understanding of diseases varies between Western and Chinese medicine. Western medicine’s understanding of diseases is based on human anatomy and pathophysiology, with clinical diagnosis relying on the patient’s subjective symptoms, physical examination, and laboratory tests. In contrast, TCM views diseases as results of imbalances in Yin and Yang, with clinical differentiation primarily based on the patient’s symptoms and signs (such as tongue and pulse), and diagnosis does not necessarily require determining the disease name but rather clarifying the “pattern”.
“Pattern” is a shorthand for evidence and symptoms; it is not merely a collection of symptoms or subjective feelings but a group of syndromes, representing TCM’s diagnosis of diseases. A “pattern” is a set of specific clinical manifestations (symptoms, signs, etc.) that encompasses the causes, affected areas, nature of the changes, and the comparative strength of pathogenic and righteous forces. A “pattern” is derived from analyzing symptoms and signs, summarizing into a concept that better explains the essence of the disease.
TCM differentiation has been developed through long-term clinical practice, with various methods including the Eight Principles, differentiation based on causes, differentiation of Qi, blood, essence, and body fluids, differentiation of organs, differentiation of defensive Qi, nutritive Qi, and blood, differentiation of the three burners, and differentiation of the six meridians. Among these, the Eight Principles is the overarching framework for all differentiation methods.
The Eight Principles of Diagnosis is based on the materials obtained from the four diagnostic methods, conducting a comprehensive analysis to explore the nature of the disease, the depth of the pathological changes, the severity of the condition, the strength of the body’s response, and the comparative strength of pathogenic and righteous forces, summarizing into eight categories of patterns: Yin, Yang, Exterior, Interior, Cold, Heat, Deficiency, and Excess. This is the fundamental method of TCM differentiation, encompassing all differentiation methods and summarizing their commonalities from their individual characteristics, playing a role in simplifying complex conditions and providing a clear framework for diagnosis.
Although the manifestations of diseases are extremely complex, they can generally be categorized into the Eight Principles. The overall categories of diseases include Yin patterns and Yang patterns; the depth of the disease can be classified as Exterior or Interior; the imbalance of Yin and Yang, with Yang excess or Yin deficiency indicating Heat patterns, and Yin deficiency or Yang excess indicating Cold patterns; the strength of pathogenic and righteous forces, with strong pathogenic Qi indicating Excess patterns and weak righteous Qi indicating Deficiency patterns. Therefore, the Eight Principles of Diagnosis analyzes the ever-changing diseases according to the simple dichotomies of Exterior and Interior, Cold and Heat, Deficiency and Excess, and Yin and Yang, revealing the contradictions within the pathological changes, thus capturing the essence of whether the condition is Exterior or Interior, Cold or Heat, Deficient or Excess, Yin or Yang. This is the fundamental spirit of the Eight Principles.
1. Exterior and Interior
Exterior and Interior indicate the depth of the disease and the severity of the condition. Generally speaking, the skin, muscles, and superficial meridians belong to the Exterior; the organs, blood vessels, bone marrow, and internal meridians belong to the Interior. Exterior patterns indicate that the disease is superficial and mild; Interior patterns indicate that the disease is deep and severe.
(1) Exterior Patterns
Exterior patterns are symptoms located superficially in the skin. Generally, they occur when external pathogenic factors invade the body through the skin and nose, leading to a series of symptoms where the righteous Qi (defensive Qi) resists the pathogenic factors, often seen in the initial stage of external diseases. Exterior patterns are characterized by sudden onset, short duration, superficial location, and mild severity. They are commonly seen in the early stages of external heat diseases, such as upper respiratory infections, acute infectious diseases, and other initial stages of infectious diseases.
Main symptoms: fever and chills (or aversion to wind), headache, thin white tongue coating, and floating pulse are the basic symptoms, often accompanied by soreness in the limbs and joints, nasal congestion, cough, and other symptoms.
Since external pathogenic factors can be either Cold or Heat, and the body’s ability to resist these factors varies, Exterior patterns can be further divided into Exterior Cold, Exterior Heat, Exterior Deficiency, and Exterior Excess patterns.
1. Exterior Cold Pattern
Main symptoms: significant aversion to cold, mild fever, pronounced pain in the head and body, no sweating, clear nasal discharge, and no thirst. The tongue is pale red, with a thin white and moist coating, and the pulse is floating and tight.
Pathogenesis: Cold pathogenic factors are constrained in the skin or superficial layers, leading to a struggle between righteous and pathogenic Qi, hence the aversion to cold and fever. The invasion of pathogenic Qi into the superficial meridians causes stagnation in the flow of defensive Qi and blood, resulting in soreness in the head, body, and limbs. The pulse is floating due to the struggle between righteous and pathogenic Qi at the surface.
Treatment principle: Warm and release the exterior.
Commonly used formula: Ma Huang Tang (Ephedra Decoction).
2. Exterior Heat Pattern
Main symptoms: significant fever, mild aversion to cold, headache, sore throat, sweating, and thick yellow nasal discharge, with thirst. The tongue is slightly red, with a thin white coating that is not moist, and the pulse is floating and rapid.
Pathogenesis: The struggle between righteous and pathogenic Qi at the surface leads to fever and aversion to cold. Heat pathogenic factors invade the defensive layer, causing sweating to escape. Heat damages body fluids, leading to thirst. The presence of heat at the surface results in a floating and rapid pulse.
Treatment principle: Cool and release the exterior.
Commonly used formula: Yin Qiao San (Honeysuckle and Forsythia Powder).
3. Exterior Deficiency Pattern
Main symptoms: Exterior symptoms with aversion to wind, sweating. The tongue is pale, with a thin white coating, and the pulse is floating and weak.
Pathogenesis: The body is constitutionally weak, and the defensive Yang is not firm, leading to aversion to wind and sweating, with a floating and weak pulse.
Treatment principle: Harmonize the nutritive and defensive Qi, release the muscles and resolve the exterior.
Commonly used formula: Gui Zhi Tang (Cinnamon Twig Decoction).
4. Exterior Excess Pattern
Main symptoms: fever, aversion to cold, body aches, and no sweating. The tongue is pale red, with a thin white coating, and the pulse is floating and strong.
Pathogenesis: The pathogenic factors are strong, and the righteous Qi is not weakened; the pathogenic factors constrain the skin, and the righteous Qi resists the pathogenic factors, leading to fever and aversion to cold without sweating, with a floating and strong pulse.
Treatment principle: Warm and release the exterior.
Commonly used formula: Ma Huang Tang (Ephedra Decoction).
Distinguishing between Exterior Cold and Exterior Heat patterns is based on the severity of aversion to cold and fever, as well as the tongue and pulse characteristics. Exterior Cold patterns present with significant aversion to cold and mild fever, while Exterior Heat patterns present with significant fever and mild aversion to cold. In addition, the tongue coating and pulse characteristics differ: Exterior Cold patterns have a thin white and moist coating with a floating and tight pulse, while Exterior Heat patterns have a thin white coating that is not moist with a floating and rapid pulse. Furthermore, Wind-Cold can transform into Heat, and Exterior Cold patterns can evolve into Interior Heat patterns after the external pathogenic factors invade the body.
Distinguishing between Exterior Deficiency and Exterior Excess patterns involves considering the patient’s constitution, with sweating without fluid loss indicating Exterior Excess, commonly seen in younger and stronger individuals, while sweating with fluid loss indicates Exterior Deficiency, often seen in older or chronically ill patients.
(2) Interior Patterns
Interior patterns, in contrast to Exterior patterns, refer to symptoms that are deeper within (involving organs, Qi, blood, bone marrow, etc.).
The causes of Interior patterns can generally be classified into three situations: first, the progression of an Exterior pattern where the exterior pathogenic factors have not been resolved and have penetrated into the Interior, affecting the organs; second, direct invasion of external pathogenic factors into the internal organs, such as abdominal cold or overconsumption of cold foods leading to Interior Cold patterns; third, internal injuries from emotional disturbances, overexertion, or dietary factors that directly impair organ function, such as dizziness and pain in the liver, palpitations and shortness of breath in the heart, cough and wheezing in the lungs, abdominal distension and diarrhea in the spleen, and low back pain and urinary retention in the kidneys. Therefore, the clinical manifestations of Interior patterns are complex, and all symptoms that are not Exterior patterns belong to Interior patterns. In external diseases, Interior patterns need to be combined with differentiation based on causes and the nutritive and defensive Qi, while in internal injuries, differentiation based on organs is primary. Interior patterns need to be distinguished as Interior Cold, Interior Heat, Interior Deficiency, and Interior Excess (discussed in the context of Cold-Heat and Deficiency-Excess differentiation).
Distinguishing between Exterior and Interior patterns is primarily based on the patient’s history, the nature of the symptoms, and changes in tongue coating and pulse. Generally, new or short-duration illnesses are more likely to be Exterior patterns, while chronic or long-duration illnesses are more likely to be Interior patterns. Fever with aversion to cold indicates an Exterior pattern; fever without aversion to cold or only cold without fever indicates an Interior pattern. Exterior patterns often show no changes in tongue coating or only slight redness at the edges and tip of the tongue; Interior patterns often exhibit abnormal tongue coatings. A floating pulse indicates an Exterior pattern, while a deep pulse indicates an Interior pattern.
(3) Half Exterior Half Interior Patterns
When the pathogenic factors are neither in the Exterior nor have fully entered the Interior, resulting in symptoms that are neither typical of Exterior nor Interior patterns, this is referred to as Half Exterior Half Interior patterns.
Main symptoms: alternating chills and fever, chest and hypochondriac fullness, bitter taste in the mouth, dry throat, irritability, nausea, loss of appetite, and dizziness. The tongue tip is red, with a yellow-white coating, and the pulse is wiry.
Pathogenesis: The struggle between righteous and pathogenic Qi occurs in the Half Exterior Half Interior region, leading to alternating chills and fever. The pathogenic factors invade this region, affecting the gallbladder meridian, resulting in fullness in the chest and hypochondria, and heat in the gallbladder causing irritability, dizziness, nausea, and loss of appetite.
Treatment principle: Harmonize and resolve the Exterior and Interior.
Commonly used formula: Xiao Chai Hu Tang (Minor Bupleurum Decoction).
(4) Concurrent Exterior and Interior Disease
Concurrent Exterior and Interior disease refers to the simultaneous presence of both Exterior and Interior patterns. There are three common situations: first, the initial onset of the disease presents both Exterior and Interior patterns; second, during the course of the disease, only Exterior patterns are present initially, but as the pathogenic factors penetrate into the Interior, Interior patterns emerge while Exterior patterns remain unresolved, also known as concurrent Exterior and Interior disease; third, if the original disease has not resolved, and a new condition arises, such as an internal injury combined with an external pathogenic factor, or an external condition leading to dietary injury, this also constitutes concurrent Exterior and Interior disease. The treatment principle is to resolve both the Exterior and Interior.
2. Cold and Heat
Cold and Heat are the two principles used to differentiate the nature of diseases, summarizing the states of Yin and Yang in the body. Generally, Cold patterns are manifestations of insufficient Yang Qi or the invasion of Cold pathogenic factors, while Heat patterns are manifestations of excessive Yang Qi or the invasion of Heat pathogenic factors. The saying goes, “Excess Yang leads to Heat, Excess Yin leads to Cold; Deficient Yang leads to Cold, Deficient Yin leads to Heat.” Differentiating Cold and Heat is the basis for using warming or cooling medicines in treatment, as the principle states, “Cold is treated with Heat, and Heat is treated with Cold.”
(1) Cold Patterns
Cold patterns are manifestations of the invasion of Yin Cold pathogenic factors (such as Cold or Dampness) or of Yang deficiency with excessive Yin, weak Yang Qi in the organs, and reduced functional activity. They can be divided into Exterior Cold patterns and Interior Cold patterns, with Exterior Cold patterns already discussed; here we refer to Interior Cold patterns.
Main symptoms: aversion to cold, cold limbs, no thirst or preference for warm drinks, pale complexion, cough with white phlegm, abdominal pain relieved by warmth, loose stools, and clear, frequent urination. The tongue is pale, with a white coating, and the pulse is deep and slow.
Pathogenesis: Yang deficiency leads to excessive Yin, causing the patient to feel cold; the spleen and stomach are cold, leading to abdominal pain relieved by warmth, and the Yang Qi is weak, resulting in a deep and slow pulse.
Treatment principle: Warm the middle and dispel Cold.
Commonly used formula: Fu Zi Li Zhong Tang (Aconite Decoction to Regulate the Middle).
(2) Heat Patterns
Heat patterns are manifestations of the invasion of Yang Heat pathogenic factors (such as Wind, Heat, or Fire) or of excessive Yang with deficient Yin, excessive Yang Qi in the organs, and increased functional activity. They can be divided into Exterior Heat patterns and Interior Heat patterns, with Exterior Heat patterns already discussed; here we refer to Interior Heat patterns.
Main symptoms: fever, no aversion to cold, irritability, thirst with a preference for cold drinks, red face and eyes, cough with yellow, thick phlegm, abdominal pain relieved by coolness, constipation, and short, red urination. The tongue is red, with a yellow coating, and the pulse is rapid.
Pathogenesis: Excessive Yang leads to fever and a preference for coolness; Heat damages body fluids, leading to thirst; short, red urination and constipation occur due to Heat. The pulse is rapid due to the presence of excess Heat.
Treatment principle: Clear Heat.
Commonly used formula: Bai Hu Tang (White Tiger Decoction).
(3) Excess Heat and Deficient Heat
Excess Heat patterns caused by the invasion of Heat pathogenic factors differ from Deficient Heat patterns caused by the depletion of Yin fluids or excessive functional activity, with different clinical manifestations and treatment principles.
Excess Heat patterns have a rapid onset and short duration, with high fever, aversion to heat, profuse sweating, delirium, and in severe cases, mania. There is thirst with a preference for drinking, cough with yellow, thick phlegm, or blood-streaked phlegm, constipation, and short, red urination. The tongue is red, with a thick yellow coating, and the pulse is rapid and forceful. Excess Heat is often caused by pathogenic Heat (such as infections). The treatment is to clear Heat and drain Fire.
Deficient Heat patterns have a slow onset and long duration, with low fever, tidal fever, night sweats, five-center heat, insomnia with vivid dreams, and dry mouth with little drinking. There is scanty, sticky phlegm, or phlegm with blood streaks, and small amounts of yellow, scanty urination. The cheeks are flushed, the tongue is red with little or no coating, and the pulse is thin and rapid. Deficient Heat is often caused by excessive functional activity. The treatment is to nourish Yin and clear Heat.
(4) True Cold and False Heat
In the critical stages of disease development, one can observe phenomena where “true Cold appears as Heat” and “true Heat appears as Cold.” Clinically, this is referred to as “True Heat with False Cold” when the essence is Heat but presents as Cold symptoms, and “True Cold with False Heat” when the essence is Cold but presents as Heat symptoms. This situation often indicates a severe condition. If the essence is not grasped, one may be misled by the false appearance, leading to misdiagnosis and mistreatment.
1. “True Cold with False Heat”: For example, patients with chronic wasting diseases often present with body heat, flushed cheeks, restlessness, black tongue coating, and a floating pulse. On the surface, it appears to have Heat symptoms, but the patient prefers warmth, is mentally exhausted and apathetic, curled up in bed, with a pale tongue and black, moist coating, and a floating but weak pulse. This indicates excessive Yin internally, with Yang constrained externally, thus the essence is still Cold, hence termed “True Cold with False Heat.” The treatment should focus on warming the Interior and restoring Yang.
2. “True Heat with False Cold”: This refers to the presence of true Heat internally while appearing as false Cold externally. For instance, in severe heat-related illnesses, one may observe a lack of expression, drowsiness, and cold hands and feet, which superficially resemble Cold patterns, but there are also signs of heat in the mouth and nose, burning sensation in the chest and abdomen, thirst with a preference for cold drinks, constipation, and short, red urination. The tongue is red, with a dry yellow coating, and the pulse is thin and rapid but forceful. This indicates internal Yang Heat that cannot express outwardly, thus the essence is Heat, hence termed “True Heat with False Cold.” The treatment should focus on clearing and draining internal Heat and promoting Yang Qi.
In general, the manifestations of Cold and Heat are superficial signs, while the internal Cold and Heat represent the essence of the condition.
To differentiate Cold patterns from Heat patterns, one should not rely solely on a single symptom or sign but should observe the overall manifestations of the disease, especially the aspects of Cold and Heat, thirst or lack of thirst, complexion, temperature of the limbs, urination and defecation, tongue appearance, and pulse characteristics. For instance, aversion to cold and preference for warmth indicates Cold, while fever, aversion to heat, and preference for coolness indicate Heat; lack of thirst indicates Cold, while thirst with a preference for drinking indicates Heat; a red complexion indicates Heat; cold hands and feet often indicate Cold, while warm limbs indicate Heat; clear, frequent urination and loose stools indicate Cold, while short, red urination and constipation indicate Heat; a pale tongue with a white coating indicates Cold, while a red tongue with a yellow coating indicates Heat, etc. From the comparison of Cold and Heat patterns, it can be seen that Cold patterns are associated with excessive Yin and often co-occur with Yang deficiency, while Heat patterns are associated with excessive Yang and often present with signs of Yin fluid deficiency.
3. Deficiency and Excess
Deficiency and Excess are the two principles used to differentiate the strength of the body’s righteous Qi and the severity of pathogenic factors. Generally, Deficiency refers to insufficient righteous Qi, and Deficiency patterns are manifestations of this insufficiency, while Excess refers to excessive pathogenic Qi, and Excess patterns are manifestations of this excess. The Suwen states, “When pathogenic Qi is strong, it is Excess; when vital Qi is depleted, it is Deficiency.” From the perspective of the comparative strength of righteous and pathogenic forces, Deficiency patterns indicate insufficient righteous Qi, but pathogenic Qi is not strong; Excess patterns indicate excessive pathogenic Qi, but righteous Qi has not yet declined, representing a stage of intense struggle between righteous and pathogenic forces. Differentiating Deficiency and Excess is the basis for determining whether to tonify (nourish Deficiency) or drain (eliminate Excess) in treatment, as the principle states, “Nourish the Deficient, drain the Excess.”
(1) Deficiency Patterns
Deficiency patterns can arise from a weak constitution (either congenital or acquired), prolonged illness damaging the righteous Qi, excessive blood loss, loss of essence, profuse sweating, or damage to the righteous Qi from external pathogenic factors, leading to “vital Qi being depleted and thus Deficient.”
Main symptoms: pale or sallow complexion, mental fatigue, physical weakness, palpitations, shortness of breath, cold limbs, or five-center heat, spontaneous sweating, night sweats, loose stools, frequent urination, pale tongue with little or no coating, and weak pulse.
Clinically, Deficiency can be categorized into Qi Deficiency, Blood Deficiency, Yin Deficiency, and Yang Deficiency, with various organ-specific Deficiency patterns (such as Lung Qi Deficiency, Heart Blood Deficiency, Liver Yin Deficiency, Spleen Qi Deficiency, Kidney Yang Deficiency, etc.). Below are the symptoms and treatment principles for Qi Deficiency, Blood Deficiency, Yin Deficiency, and Yang Deficiency. The organ-specific Deficiency patterns will be discussed in the context of organ differentiation.
Common symptoms of Qi Deficiency and Yang Deficiency include: pale or sallow complexion, mental fatigue, physical weakness, low voice, spontaneous sweating, reduced appetite, pale and swollen tongue, and weak pulse. The difference is that Qi Deficiency presents with shortness of breath, fatigue, and increased breathlessness with exertion, while the pulse is weak. The treatment principle is to tonify Qi, commonly using Si Jun Zi Tang (Four Gentlemen Decoction). Yang Deficiency presents with aversion to cold, cold limbs, clear, frequent urination, and diarrhea with clear stools, with a slow pulse. The treatment principle is to tonify Yang, commonly using Shen Qi Wan (Kidney Qi Pill) or Ren Shen Rong Wan (Ginseng and Deer Antler Pill).
Common symptoms of Blood Deficiency and Yin Deficiency include: weight loss, dizziness, blurred vision, insomnia, palpitations, and thin pulse. The difference is that Blood Deficiency presents with a pale, dull complexion or sallow skin, numbness in the hands and feet, pale lips and nails, pale tongue, and weak pulse. The treatment principle is to nourish Blood, commonly using Si Wu Tang (Four Substance Decoction). Yin Deficiency presents with low-grade fever or tidal fever, flushed cheeks, five-center heat, dry mouth, dry throat, night sweats, red tongue, thin or cracked tongue, little or no coating, and thin rapid pulse. The treatment principle is to nourish Yin, commonly using Liu Wei Di Huang Wan (Six Flavor Rehmannia Pill).
From the above, it can be seen that Qi Deficiency and Yang Deficiency are both associated with insufficient Yang Qi, thus presenting similar clinical manifestations, including pale complexion, fatigue, spontaneous sweating, etc. However, they also have distinctions: Qi Deficiency is Deficient without “Cold signs,” while Yang Deficiency is Deficient with “Cold signs”—aversion to cold, cold limbs, and slow pulse. Blood Deficiency and Yin Deficiency are both associated with insufficient Yin fluids, thus presenting similar clinical manifestations, including weight loss, dizziness, palpitations, and insomnia. However, they also have distinctions: Blood Deficiency is Deficient without “Heat signs,” while Yin Deficiency is characterized by insufficient Yin fluids that cannot restrain Yang Qi, leading to excessive Yang—thus presenting as Deficient with “Heat signs”—low-grade fever or tidal fever, dry mouth, and dry throat.
(2) Excess Patterns
Excess patterns can arise from a strong constitution in the patient, leading to acute illness due to external pathogenic factors, or from dysfunction of the organs leading to the accumulation of pathological products within the body, such as Qi stagnation, blood stasis, phlegm-damp accumulation, parasitic infections, or food stagnation.
Clinical manifestations vary based on the nature of the pathogenic factors and the organs affected, characterized by strong pathogenic Qi and weak righteous Qi, with intense struggle between the two. Common symptoms include high fever, flushed face, irritability, delirium, loud voice, abdominal distension and pain with tenderness, excessive phlegm, constipation, difficulty urinating, or the presence of blood stasis, edema, food stagnation, or parasitic infections, with thick greasy tongue coating and strong pulse.
Treatment principle: The main method for treating Excess patterns is to drain and attack the pathogenic factors, as the principle states, “Excess should be drained.” However, different methods of draining, such as clearing Heat, promoting bowel movements, draining water, resolving phlegm, regulating Qi, invigorating blood, and eliminating stagnation, will be discussed in relevant chapters.
Distinguishing between Deficiency and Excess patterns can be considered from the following aspects: regarding the time of onset, new or acute illnesses or short-duration illnesses are often Excess patterns, while chronic or long-duration illnesses are often Deficiency patterns; regarding the cause, external pathogenic factors often indicate Excess patterns, while internal injuries often indicate Deficiency patterns; regarding constitution, younger and stronger individuals are more likely to present with Excess patterns, while older or weaker individuals are more likely to present with Deficiency patterns; regarding clinical symptoms and signs, the following distinctions can be made:
Deficiency patterns: pale, sallow, or dull complexion, fatigue, low voice, tenderness to pressure, pale tongue with little or no coating, and weak pulse. Treatment principle: Nourish Deficiency.
Excess patterns: flushed face, irritability, delirium, loud voice, severe pain with tenderness, red tongue with thick yellow coating, and strong pulse. Treatment principle: Drain Excess.
4. Yin and Yang
Yin and Yang are the two principles used to differentiate the nature of diseases, serving as the overarching framework for the Eight Principles, summarizing the Exterior and Interior, Cold and Heat, and Deficiency and Excess. The “Liu Jing: Yin and Yang” states, “In human diseases, there must be a basis, either rooted in Yin or in Yang. Although the manifestations are numerous, their essence is one,” indicating that although symptoms may be complex and varied, they ultimately fall into the two categories of Yin and Yang, and thus the key to diagnosing diseases must first clarify whether they belong to Yin or Yang. Therefore, Yin and Yang serve as the overarching framework for the Eight Principles, generally categorizing Exterior, Excess, and Heat patterns as Yang patterns, while Interior, Deficiency, and Cold patterns as Yin patterns. Clinically, Yin patterns often refer to Interior Deficiency Cold patterns, while Yang patterns often refer to Interior Excess Heat patterns.
(1) Yin Patterns
Yin patterns are characterized by a deficiency of Yang Qi and an excess of Yin. Generally, Yin patterns present with Cold signs, such as aversion to cold, absence of fever, cold limbs, mental fatigue, and a deep, weak or slow pulse. They arise from the low function of organs and a weakened response of the body, often seen in older or weaker individuals or those with chronic illnesses, presenting a picture of Deficient Cold.
(2) Yang Patterns
Yang patterns are characterized by an excess of Yang Qi and the absence of deficiency in righteous Qi. Generally, Yang patterns present with Heat signs, such as fever, aversion to heat, warm limbs, irritability, thirst, and a rapid, strong pulse. They arise from the hyperfunction of organs and are often seen in robust individuals, presenting a picture of Excess Heat.
(3) Loss of Yin and Loss of Yang
Loss of Yin and Loss of Yang are two dangerous patterns that can occur during the disease process, often seen in cases of high fever, profuse sweating, severe vomiting and diarrhea, or excessive blood loss, leading to rapid loss of Yin fluids or Yang Qi, commonly seen in patients in shock. Although Loss of Yin and Loss of Yang fall under the category of Deficiency patterns, they are distinguished from general Deficiency patterns due to their special and critical nature.
Clinical manifestations of Loss of Yin and Loss of Yang, in addition to various critical symptoms of the underlying disease, often present with varying degrees of sweating. However, the sweating in Loss of Yin is hot and sticky, accompanied by hot skin, warm hands and feet, thirst with a preference for drinking, and a rapid, thin pulse that is weak upon pressure, indicating depletion of Yin and extreme Yang; while the sweating in Loss of Yang is profuse and cool, accompanied by aversion to cold, lethargy, cold limbs, mental fatigue, and a pulse that is weak and nearly absent, indicating loss of Yang and excess of Yin. Since Yin and Yang are interdependent, depletion of Yin fluids leads to the dispersion of Yang Qi, while depletion of Yang Qi leads to the inability of Yin fluids to generate, thus the clinical manifestations of Loss of Yin and Loss of Yang are difficult to separate, with rapid transformations occurring between them, only differing in their order of precedence.
The treatment for both Loss of Yin and Loss of Yang focuses on supporting the righteous Qi and stabilizing the condition. For Loss of Yin, the approach is to nourish Qi, restrain Yin, and restore fluids, greatly tonifying the original Qi to generate Yin fluids and prevent Loss of Yang, commonly using Sheng Mai San (Generate the Pulse Powder); for Loss of Yang, the approach is to nourish Qi, stabilize the condition, and restore Yang, commonly using Du Shen Tang (Ginseng Decoction) or Shen Fu Tang (Ginseng and Aconite Decoction).
The distinctions between the Eight Principles of Exterior and Interior, Cold and Heat, Deficiency and Excess, and Yin and Yang are not simple, isolated, or static; rather, they are complex, interrelated, and transformable. In summary, the Eight Principles exhibit relationships of “coexistence,” “intermingling,” and “transformation.”
(1) Coexistence
“Coexistence” refers to the simultaneous presence of two or more principles, such as in the early stages of external heat diseases, where both Exterior patterns and further differentiation into Cold or Heat may be observed, thus leading to classifications of Exterior Cold or Exterior Heat patterns; in chronic diseases, Deficiency patterns may also require further differentiation into Deficient Cold or Deficient Heat patterns. The appearance of coexistence patterns should not be viewed uniformly, as there are primary and secondary relationships; for example, both Exterior Cold and Exterior Heat patterns are primarily Exterior patterns, with Cold or Heat being secondary to the Exterior pattern, thus treatment should primarily focus on resolving the Exterior, using warming or cooling methods as appropriate; similarly, both Deficient Cold and Deficient Heat patterns are primarily Deficiency patterns, with Cold or Heat being secondary to the Deficiency pattern, thus treatment should primarily focus on tonifying the Deficiency, using warming or nourishing methods as appropriate. In cases of coexistence between Exterior and Interior, the primary pattern should be determined based on the specific condition.
(2) Intermingling
“Intermingling” refers to the simultaneous presence of opposing symptoms from two principles, such as Cold and Heat intermingling, Deficiency and Excess intermingling, or Exterior and Interior intermingling (commonly referred to as concurrent Exterior and Interior disease). Additionally, during the progression of a disease, false appearances may arise, such as true Heat appearing as false Cold or true Cold appearing as false Heat. Therefore, during the differentiation process, careful observation and comprehensive analysis are essential to discern the truth and grasp the essence, avoiding misdiagnosis and mistreatment that could delay the condition.
(3) Transformation
“Transformation” refers to the phenomenon where symptoms of one principle transform into those of its opposite. The relationships between Exterior and Interior, Cold and Heat, Deficiency and Excess, and Yin and Yang are not only opposing but can also transform into one another under certain conditions. For example, an external Wind-Cold pattern presenting with aversion to cold and fever may, due to disease progression or improper treatment, lead to the pathogenic factors penetrating into the Interior, resulting in a transformation from Cold to Heat, ultimately evolving from an Exterior Cold pattern to an Interior Heat pattern; similarly, Excess patterns may transform into Deficiency patterns due to misdiagnosis or inadequate treatment, where although the pathogenic Qi diminishes, the righteous Qi is also harmed, gradually transforming into a Deficiency pattern. Conversely, Deficiency patterns may lead to the generation of phlegm, dampness, Qi stagnation, or blood stasis, resulting in various Excess patterns. Transformation can only occur under specific conditions, and during differentiation, it is crucial to continuously assess changes in the pathogenesis, timely diagnose and treat, and prevent the disease from worsening while promoting recovery.
When applying the Eight Principles of Diagnosis, one should first differentiate between Exterior and Interior to determine the location of the disease; then differentiate Cold and Heat, Deficiency and Excess, to clarify the nature of the disease and understand the comparative strength of the righteous and pathogenic forces; finally, one can use Yin and Yang for a comprehensive summary.