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I. Exterior & interior | II.Cold & heat | III Dificiency & excess | IV. Yin & Yang

Syndrome differentiation according to the eight principles

The content of the eight principles was discussed early in the Huang Ti Nei Ching (The Yellow Emperor's Medicine Classic). However it was not until the Ming dynasty, that physicians used it regularly in diagnosis of patients. For example Zhang San Xi wrote in the book Yi Xue Liu Yao (Six Essence of Medicine): "The ancient physicians treated on the basis of eight methods. These were yin, yang, exterior, interior, cold, heat, deficiency (xu) and excess (shi). In addition, qi, blood, phlegm and fire were also included within these." Wang Zhi Zhong, also from the Ming dynasty, said in the book 'Dong Yuan Xian Sheng Shang Han Zheng Mai: Juan Yi': "If the doctor does not vary from the eight words (principles), then people will not be killed." Today, TCM doctors still use the eight principles to understand the location and nature of pathological changes, the course of the disease and the strength of the evil and the vital energy (qi). It serves as the guiding rules for all syndrome identification.
Summary on Eight Principles

The concept of this method is that signs and symptoms of a disease or illness can be generalized according to the eight principles. For instance, the location or severity of the disease may be termed as interior or exterior; the nature of the disease may be divided into cold or heat syndromes; and the condition of the disease may belong to either the excess(shi) or deficiency(xu) syndromes. The interior, cold and deficiency syndromes are categorized as yin; the exterior, heat and excessive syndromes are categorized as yang. As a whole, yin and yang is a compendium of the other six principles. Although these four pairs of categories have different characteristics, the patterns sometimes interact.

Exterior and interior
  Exterior and interior determine the severity of the disease and its location. If a disease occurs in the skin, hair or flesh, it is usually ascribed to an exterior type; if the disease occurs in the organs; it is ascribed to an interior type. When the disease is in the exterior, the disease evil is shallow and the disease is light. If the disease is in the interior, the disease evil has moved inward and the disease is strong. Since exterior and interior relate to the depth of the diseased area and generalize the direction of the development of the disease; it is especially important for diagnosing exogenous diseases, which are diseases or illnesses whose cause originate from outside of the body.
   
 
  Syndromes of exterior type
This refers to conditions resulting from an invasion of exogenous pathogens in the superficial portion of the body. These conditions are marked by sudden onset, short duration, and are often seen in the early stages of exogenous diseases. Their major manifestations are aversion to cold or wind, fever, a thin tongue coating and a floating pulse. Some of the accompanying symptoms are headache, general aches, nasal congestion and runny nose, itching or pain of the throat, and cough.
   
  Syndromes of interior type
This refers to pathology changes deep into the interior portion of the body that affect organs, bone marrow, qi (vital energy) and blood. Opposite to the exterior type, the clinical manifestations are complex and broad and may vary according to the invading pathogenic factors and the body resistance of the patient. These syndromes are discussed more fully in the section of Syndromes Differentiation According to Organs (zang-fu). There are no clinical manifestations of aversion to wind or cold or the presence of a floating pulse, but tongue and tongue fur changes are usually present.
   
Disease and illness symptoms usually change over time; and therefore, so can the type of syndrome a person experiences. Exterior and interior syndromes can mutually convert to simultaneous exterior and interior type or half exterior-half interior type.

The exterior and interior syndromes can further be categorized with other principles in regards to their characteristics.

Classification of exterior & interior syndromes
Exterior Interior
Cold type Fever, aversion to cold, general aching, no sweating, floating and tense pulse, thin white tongue coating. Aversion to cold, cold limbs, pallor, absence of thirst, nausea, vomiting, diarrhea, clear profuse urine, deep and slow pulse, pale and slimy tongue.
Heat type Fever, slight aversion to wind or cold, sweating, thirst, sore throat, floating and rapid pulse, red tongue. High fever, sweating, thirst, preference for cold drinks, irritability and restlessness, flushed face, abdominal distention, constipation, deep yellow scanty urine, rapid and excess pulse, red tongue with yellow and dry coating, surging and rapid pulse.
Deficiency (xu) type Aversion to wind, sweating, floating and slow and forceless pulse. The tongue is slightly bulky. Feeble breathing, apathy, general weakness, poor appetite, palpitation, dizziness, abdominal pain and preference for pressure, incontinence, deep and weak pulse, the tongue is pale and bulky and tender with a white coating.
Excess (shi) type Aversion to cold, lack of sweating, general aching, floating and tense pulse, white tongue coating. Coarse breathing, sonorous voice, irritability, fullness in chest, abdominal distention and pain when pressed, constipation, difficulty urinating, deep and excess pulse, rough tongue with thick coating.


 
Cold and heat
  Cold and heat are two commonly seen symptoms from a TCM viewpoint. They reflect the relative abundance and depletion of yin and yang of the body and relate to two different natures of disease.
 
   
  Syndromes of cold type
A cold syndrome is a recessive condition resulting from exposure to exogenous cold or a constitutional (originating from the body itself) yang deficiency. The major symptoms are a pale complexion, aversion to cold and preference for warmth, inability to taste, cold limbs, clear and profuse urine and loose stools. On examination, there is a pale tongue with a white moist coating and a slow or tense pulse.
   
  Syndromes of heat type
Heat syndromes are excitatory conditions caused by invasion of exogenous heat or constitutional (originating from the body itself) yin deficiency. The major symptoms are a red complexion, fever, sweating, irritability, thirst preference for cold drinks, constipation and deep yellow and scanty urine. On examination, the tongue is red with yellow and dry coating and the pulse is rapid.
   
  Although cold and heat are opposite in nature, they are closely related in clinical presentations and can exist simultaneously, manifesting as complicated syndromes of cold and heat. In certain conditions, they can also be transformed into each other. When the disease has developed to a very severe stage, syndromes of true heat and false cold or true cold and false heat may appear. For example, diseases caused by pathogenic heat, summer heat or dryness are heat syndromes, while those caused by pathogenic cold are cold syndromes, and the latter are likely to turn into the former.
 
Deficiency(xu) and excess(shi)
  Deficiency(xu) and excess(shi) are two principles that help analyze and generalize the opposing forces between the body resistance and pathogenic factors during the course of a disease. Generally, deficiency (xu) types indicate conditions caused by the weakness and insufficiency of body resistance. Excess(shi) types refer to conditions induced by an overabundance of exogenous pathogens.
 
   
  Syndromes of deficiency(xu) type
These refer to conditions due to an insufficiency of the body's disease preventing forces as opposed to excess exogenous pathogenic factors invading the body. Owing to various disease preventing factors inside the body, patterns of deficiency(xu) can be further classified into qi deficiency, blood deficiency, yang deficiency, yin deficiency and body fluid deficiency. Each has various clinical manifestations. The general deficiency(xu) syndromes include fatigue, low-spiritedness, skinny appearance, sluggishness, pale complexion, palpitation, shortness of breath, spontaneous sweating, night sweating, insomnia, poor memory, loose stools and frequent urination or incontinence. On examination, there is a pale tongue without coating, thready and weak pulse.
   
  Syndromes of excess(shi) type
These refer to conditions due to an accumulation of excessive exogenous pathogenic factors when the body's resistance has not yet weakened. This results in hyperactive, precipitating struggles between the two forces. Besides exogenous pathogens invasion, excess(shi) type syndromes may also be caused by endogenous damage such as qi stagnation, blood stasis, phlegm obstruction or stagnancy of water or body fluid flow. The general excess(shi) syndromes can present with complex symptoms such as hardiness, agitation, sonorous voice, coarse breathing, distension and fullness in the chest and abdomen, abdominal pain that becomes worse when pressed, constipation and urinary difficulty. On examination there may be a thick and sticky tongue coating and excess pulse. The patient's body may still remain strong and vigorous.

In reality, conditions that mix deficiency(xu) and excess(shi) types usually appear, or they may inter-changeable. For example, individuals who suffer from stagnation in blood and qi (vital energy) have an excess(shi) type syndrome; however, when most of the body's disease preventing forces become weakened an individual can shift to a mixed condition.

TCM clarifies heat and cold syndromes very precisely. According to their abundance or depletion of yin and yang, they are associated with another category - the deficiency(xu) and excess(shi) syndromes. Excess(shi) type and heat evils often intermingle, while a deficiency(shi) type is often associated with cold evils.

Classification of cold and heat syndromes according to deficiency(xu) and excess(shi) principles
Main presentations Causes
Cold-excess type Acute onset, aversion to cold, cold limbs, excess sputum, asthmatic breathing, abdominal pain that becomes worse when pressed and constipation. The pulse is deep or taut and tense; the tongue fur is white, greasy and thick and its color may appear green-blue or purple. Invasion by exogenous cold, over-eating food with cold energies.
Cold-deficient type Gradual onset, aversion to cold, cold limbs, shortness breath, general weakness, abdominal pain that becomes worse when pressed, loose stools and clear profuse urine. The pulse is weak, deep and slow; the tongue is pale, bulky and tender. Long term illness leads to yang-qi depletion and relative excess of yin.
Heat-excess type Acute onset, short duration, persistent high fever, thirst, flushed face, fullness and distending pain in abdomen that becomes worse when pressed, unconsciousness in very serious cases, constipation, pain on urination and deep yellow urine. On examination, there is a rapid and excess pulse, and the tongue is red or deep red with a dry yellow coating. Heat or fire evil invasion, over-eating spicy food or food with hot energies, excessive yang qi in the body.
Heat-deficient type Gradual onset, long duration; fluctuant low-grade fever; night and spontaneous sweating, bone pain, dry mouth, skinny appearance, shortness breath and general weakness. When examining the hand, the palm side is hotter than the backside. The pulse is thready and rapid; the tongue is red with little fur, or the tongue may be bulky and tender. Long-term illness, leads to depletion of yin fluid and relative excess in yang. These are also called virtual fire production" or "yin vacuity internal heat."


Yin and Yang
  Yin and yang is the main guiding principle of the other six principles, i.e., exterior, heat and deficiency(xu) belong to the category of yang, while interior, cold, and excess(shi) belong to yin. In clinical diagnosis, physicians usually first differentiate whether the syndrome is ascribed to yin or ascribed to yang, because although the syndrome may be complex with many changes, it still does not depart from the two major categories. Yang types are characterized by excitation, restlessness, hyperactivity and optimism, while those characterized by inhibition, quietude, deterioration and gloominess are categorized as yin type.

The yin yang concept is also applied to explain the changes in the organs and tissues. See article on "The Yin Yang Theory". They can be detailed as the yin deficiency, yang deficiency, collapse of yin, collapse of yang.