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The Application of Yin Yang Theory in Traditional Chinese Medicine

Application in human body structures

Traditional Chinese Medicine (TCM) believes the human body has organic unity. The sense of unity is based on the opposing and complementary relationships of yin and yang. The body's organs and tissues can be classified according to yin yang theory based on their functions and locations. The upper body belongs to yang while the lower body belongs to yin. Other yin yang pairs in the body include the interior (yin) versus the exterior (yang), the front (Yin) versus the back (yang), the inside (yin) versus the outside (yang) of the limbs and the five yin organs versus the six yang organs. Each organ can also be further divided into yin and yang aspects such as heart yin and heart yang and kidney yin and kidney yang.

Physiological application

TCM believes health is achieved when yin and yang are in harmony. As already mentioned, the body's physical form belongs to yin while the body's activities or functions belong to yang. Because both the body's physical form and functions are dynamically balanced, they mutually restrict and depend on one another. The body cannot function if it doesn't have a physical form in which to perform them. Furthermore, physiological functions can consume certain physical forms (material) and metabolize these materials to obtain energy.

Pathological application

TCM believes yin yang disharmony is the cause of disease and physiological disorders. Disharmony means the proportions of yin and yang are unequal and unbalanced. When one aspect is deficient, the other is in excess. There are many factors that cause yin and yang disharmony, but they are all related to the "evils" (outside influences that cause disease) and the flow of qi throughout the body. When a person has normal qi flow, their body functions well and has good immunity allowing them to recover easier from illness. Normal qi is composed of yang qi (physiological functions and energy) and yin fluid (physical form and the physiological fluid of body) while the "pernicious evils" are composed of six evils. Cold and dampness belong to yin evils while wind, dryness, summer heat, and fire belong to yang evils. Hence in TCM, disease results from either a deficiency of normal qi (deficiency of yin fluid or a deficiency of yang qi) or an excess of the "pernicious evils" (excess of yin evils or yang evils). The conflict between resuming normal qi and getting rid of the "pernicious evils" is what allows the disease to either progress or transform back to a healthy state. By applying the yin yang theory to treat and diagnose diseases, yin yang harmony can be restored and health maintained.

Diagnostic application

TCM diagnoses patients according to their disharmony pattern. Preliminarily, all patterns are classified into a system known as the "eight principal patterns." The "eight principal patterns" contain four pattern pairs: interior and exterior, cold and heat, deficiency and excess, and yin and yang. Among the eight patterns, yin and yang are the most fundamental and essential pattern pair. (See Table 2.). Generally speaking, yang signs are associated with excitatory, active, hot, progressing externally and developing upward and improving manifestations. Yin signs, on the other hand, are associated with inhibitory, resting, passive, cold, progressing internally and developing downward and worsening manifestations. Table 3 illustrates the clinical signs of yin and yang patterns.

Table 2 Eight Principal Disharmony Patterns
  Disharmony Pattern Yin/Yang Manifestations
1 Exterior Yang An exterior pattern is generated by "external influences" such as wind and cold. (i.e. common cold)
2 Interior Yin An interior pattern is generated by internal disharmony such as a disorder of organ function.
3 Cold Yin A cold pattern is manifested by the signs such as a pale face, cold limbs, aversion to cold, clear urine, or watery stools. The signs are usually related to non-excitatory physiological functions.
4 Heat Yang A heat pattern is manifested by signs of a red face, high fever, dislike of heat, dark urine, or constipation. The signs are usually related to excitatory physiological functions.
5 Deficiency Yin Signs of frail and weak movements, tiredness, shortness of breath, low voice, or dizziness indicate a deficiency pattern. The signs are usually related to lack of energy of normal functions.
6 Excess Yang An excess pattern exhibits signs of heavy movements, heavy and coarse respiration, or discomfort when touched with pressure. The signs are usually related to an excess/accumulation of evils/metabolic waste.
7 Yin Yin General pattern groups for Yin manifestations include interior, cold and deficiency patterns.
8 Yang Yang General pattern groups for Yang manifestations include exterior, heat and excess patterns.

Table 3 Yin and Yang signs in the body

Body signs

Yang signs Yin signs
Face Red face, fever, hot feeling, agitated and active manner Pale face, low spirit, feels cold, cold limbs, tired and weak,
Voice Coarse and strong voice, coarse breath, dry moth, thirst Low voice, reduced appetite, no taste in mouth, little thirst
Urine Constipation with awkward smell, dark urine Copious and clear urine
Tongue Red and scarlet tongue or yellow and black moss present on tongue Pale and swollen tongue material
Pulse Rapid and floating, flooded and strong, slippery and full pulse Slow and sinking, weak, frail pulse