Tongue coating diagnosis Principle and why is reliable?

Principle

The principle of tongue coating diagnosis is based on TCM's holistic concept and the theory of pattern differentiation and treatment. TCM views the body as an organic whole, with the organs, Qi, blood, and body fluids interconnected, working together to maintain life activities. 

The tongue coating reflects the internal and overall state of the body, and changes in the tongue's appearance (including coating and texture) reveal internal changes. Tongue coating diagnosis uses these changes to identify the nature and progression of diseases, guiding treatment.

Tongue coating diagnosis is considered reliable primarily because it reflects the internal organs' and the body's overall health. It is simple, direct, and allows practitioners to make preliminary judgments about the condition and formulate appropriate treatment plans by observing changes in the tongue coating.

Tongue coating diagnosis is an important method in Traditional Chinese Medicine (TCM) and is considered reliable for several reasons:

1. Relationship Between Tongue Coating and Internal Organs

• TCM believes that the tongue is an external manifestation of the internal organs. Changes in the tongue coating can reflect the health of the internal organs. Imbalances in different organ functions are manifested on the surface of the tongue through the meridians, leading to changes in the tongue coating. For instance, the digestive system's condition can be reflected in the thickness, color, and moisture of the tongue coating. Therefore, tongue coating can provide clues about the health of the internal organs.

2. Mechanism of Tongue Coating Formation

• The formation of tongue coating is closely related to the body's Qi, blood, body fluids, and organ functions. Under normal conditions, the tongue coating is produced by the stomach Qi steaming the body fluids. The thickness, color, and texture of the tongue coating can reflect the strength of stomach Qi, the presence of dampness, and the manifestations of heat or cold syndromes. For example, a thick, greasy coating might indicate damp-heat or phlegm-dampness in the body, while a thin white coating is often seen in normal or mild illness states.

3. Reflection of Disease in Tongue Coating

• In pathological conditions, changes in tongue coating can reflect the nature of pathogenic factors, the depth of disease, and the progression of illness. TCM uses the observation of the tongue coating's color, shape, thickness, moisture, and exfoliation to determine the cold, heat, deficiency, and excess of a disease, the severity of the condition, and the course of the disease. For example, a change from thin to thick coating may indicate worsening illness, while a change from thick to thin may suggest improvement.

4. Correlation with Overall Body Condition

• Tongue coating not only reflects local changes but also provides a comprehensive view of the body's condition. The changes in tongue coating often align with the body's overall pathological state, allowing TCM practitioners to diagnose systemic diseases and apply differentiated treatments.

5. Simplicity and Directness

• Tongue coating diagnosis is simple and direct, requiring no complex equipment. Practitioners can quickly gather information through visual observation. The changes in tongue coating are usually noticeable and easy to capture, making it particularly useful for the preliminary diagnosis of new patients.

Tongue Body:

• Shape: A normal tongue body is neither swollen nor thin, and it is soft, flexible, and moist. If the tongue body is firm and aged-looking, regardless of the coating, the condition is typically excess (Shi). If the tongue is swollen, delicate, or has teeth marks on the edges or tip, regardless of the coating color, the condition is often deficiency (Xu). Papillae (prickles) on the tongue indicate internal heat; cracks on the tongue suggest either excess heat or a deficiency of Yin and blood. A swollen, enlarged tongue is usually caused by internal damp-heat. A deep red, stiff tongue with unclear speech often indicates damage to body fluids from heat, or heat entering the pericardium. Protruding and wriggling of the tongue usually indicate heat in the heart and spleen.

• Color: A normal tongue is light red, fresh, and moist. A pale tongue without coating usually indicates Qi and blood deficiency. A bright red tongue often suggests heat or excess conditions. A red, dry tongue without coating usually indicates depletion of body fluids. A fresh red tongue with prickles indicates intense heat in the blood. A deep red tongue color commonly signifies heat in the blood. A purple tongue is usually a sign of blood stasis.

Tongue Coating:

• Normal tongue coating is thin, white, and clean, with a moderate level of moisture. Tongue coating typically thickens as the illness progresses. The moisture level of the coating can indicate the state of body fluids. A greasy or thick coating usually indicates dampness and turbidity in the stomach and intestines. A white coating often suggests external wind-cold. Yellow coating indicates that the heat disease is deepening. White, greasy coating often suggests cold-dampness, while yellow, greasy coating suggests damp-heat. A black, moist coating usually indicates Yang deficiency and cold syndrome, while a black, dry coating often indicates damage to body fluids due to heat.

Additional Note: It is important to distinguish the tongue's natural appearance from any artificial discoloration caused by food or drink.