“Tongue diagnosis” is an important component of Traditional Chinese Medicine (TCM) diagnosis, as TCM believes that “the tongue is the sprout of the heart” and “the coating is the root of the stomach qi.” The internal organs of the human body can be directly reflected on the tongue when there are pathological changes. Therefore, mastering some basic techniques of “tongue diagnosis” can help you better understand your health status and detect diseases early.
Observing the Tongue for Health
In ancient literature, there are many descriptions and discussions about tongue appearances. For example, the “Tongue Diagnosis Compendium” states: “The tongue is the sprout of the heart, its color should be red, not overly bright; its texture should be moist, not smooth; its appearance should be hairy, without thorns. It must have a light red color with a thin white coating, which indicates a healthy tongue.” It also states: “A light red tongue color is the normal condition of a healthy person; red indicates heart qi, while pale indicates stomach qi.” The “General Discussion on Tongue Diagnosis” mentions: “The tongue is the sprout of the heart, which belongs to fire; its color is red. The heart resides in the lung, which belongs to metal; its color is white. Therefore, the tongue should be light red, with a slightly white coating. The red must be moist and full, and the white must be thin and not thick, or slightly thick with spots. Both should be moderately moist, neither slippery nor dry. This is a tongue without disease, representing the fire hidden within metal.” The “Guide to Tongue Diagnosis: The Principles of Tongue Coating Formation” states: “The tongue coating is formed by the stomach steaming and the spleen dampness rising.” This indicates that the formation of tongue appearances is related to the functions of the heart, lungs, spleen, and stomach. A normal tongue appearance indicates strong stomach qi, abundant qi and blood, and normal organ functions.
How to Observe Tongue Appearance
When observing the tongue, it is essential to be calm and relaxed, preferably in a well-lit natural light setting. First, face the light so that it directly illuminates the oral cavity to avoid affecting the recognition of tongue quality and coating color. When sticking out the tongue, do so slowly, without haste or tension. After extending it, place it against your lips and try to relax. Note that the shape of the tongue when extended is actually an observation of its state.
The main characteristics of a normal tongue appearance are: the tongue body is soft and elastic, light red in color, vibrant, and covered with a thin white coating that is moderately moist. The blood vessels at the root of the tongue are of moderate thickness and smooth, and the length does not exceed half of the tongue’s base. TCM divides the tongue into the tip, middle, root, and sides. TCM believes that the tip belongs to the heart and lungs, the middle belongs to the spleen and stomach, the root belongs to the kidneys, and the sides belong to the liver and gallbladder.
Observations should include tongue quality, coating, papillae, and the meridians at the tongue’s base. Tongue quality includes the size, shape, color, thickness, hardness, and surface cracks of the tongue; tongue coating includes color, moisture, thickness, and whether there are spots; the blood vessels at the tongue’s base are primarily distinguished by length and thickness; the papillae depend on size and color.
The Relationship Between Tongue Appearance and Disease
(1) Excessively white coating: Often indicates cold syndromes; a thin and slippery coating is usually due to external wind-cold, while a thick white and slippery coating often indicates cold dampness or phlegm.
(2) Yellow coating: Generally seen in the course of heat diseases, indicating a fierce struggle between evil and righteous qi, with the disease having penetrated deeply, and the evil has transformed into heat.
(3) Black coating: Mainly caused by the proliferation of filiform papillae turning black, which can vary from brown-black, gray-black, charred black to pitch black. TCM believes that the presence of this coating indicates a long-standing illness with complex and severe pathology.
(4) Grayish-white or grayish-thin slippery coating: Often indicates internal cold, typically seen in cases of weakness combined with heat diseases, or signs of prolonged illness combined with digestive disorders.
(5) A uniformly pale purple tongue with a bluish tint: Smooth and without coating indicates a yang syndrome of typhoid fever. A brown coating indicates intestinal obstruction.
The Relationship Between Tongue State and Disease
(1) Mirror tongue: The tongue surface has no coating and is smooth like a mirror. Mild cases indicate malnutrition or a lack of iron or vitamin B2; severe cases indicate a significant deficiency of body fluids, indicating a serious condition.
(2) Heart-shaped tongue: A small area in the middle of the tongue has lost its coating, often indicating a deficiency of nutrients in the body.
(3) Beef tongue: The tongue is dark red, and the coating is smooth and peeled, resembling beef. Beef tongue is commonly seen in patients with malignant anemia.
(4) Punctate tongue: Refers to the presence of many red spots protruding from the tongue surface, resembling strawberry fruit. Punctate spots appearing on the tip or sides of the tongue indicate heat, which can be seen in various febrile infectious diseases or patients with extensive burns; if punctate spots appear in the middle of the tongue, it often indicates a more severe heat toxin or heat entering the blood level, which can easily lead to shock or coma. Insomnia, constipation, or those under stress at night, as well as vitamin deficiencies, malnutrition, and cortical dysfunction, may also present with red punctate spots on the tongue surface.
(5) Cracked tongue: The surface of the tongue has deep and shallow cracks, as well as cracks and wrinkles in various directions. Shallow cracks on the tongue surface are mainly due to atrophy of the tongue mucosa, while deep cracks indicate more severe atrophic changes.
(6) Rigid tongue: The tongue body is neither swollen nor shrunk, but is stiff and loses its usual softness and flexibility, also known as “stiff tongue.” A stiff tongue is often seen in more severe conditions, such as coma or convulsions.
(7) Quivering tongue: When the tongue is extended, it shows involuntary tremors, which can be seen in high fever, hyperthyroidism, hypertension, and certain neurological disorders.
(8) Flaccid tongue: A soft tongue is a normal state, but if the tongue is excessively soft and weak, making it difficult to move or extend, it is called a flaccid tongue. Flaccidity in any part of the body has various causes, but the main reason is the lack of nourishment in the muscles and tendons; a flaccid tongue with a pale color is often due to deficiency of heart and spleen qi and blood, insufficient to nourish the tongue’s tendons; a flaccid tongue with a red color indicates extreme heat damaging fluids, or yin deficiency with excessive fire, leading to deficiency of qi and fluids in the stomach and kidneys, resulting in the tongue’s tendons being deprived of nourishment. A flaccid tongue with a dry red color and no fluids indicates extreme deficiency of kidney yin, representing a severe condition.
(9) Deviated tongue: When the tongue is extended, the tip deviates to one side, either left or right, known as a deviated tongue. The tongue muscles on the affected side are paralyzed and weak, causing the tongue to deviate when extended. This condition is often seen in strokes, i.e., cerebrovascular accidents. In cases of localized disease, it may be due to compression or damage to the hypoglossal nerve or facial nerve. For unexplained tongue deviation, caution should be exercised to rule out intracranial lesions.
Considerations for Tongue Diagnosis
(1) Influence of Light
The intensity and tone of light greatly affect color perception. Tongue observation should ideally be done in bright and soft natural light during the day; if at night or in dark places, fluorescent light is preferable, with the light directly illuminating the tongue surface, avoiding colored doors or windows.
(2) Influence of Diet or Medications
Diet and medications can cause changes in tongue appearance; excessively cold or hot foods and stimulating foods can alter tongue color. Overeating rich foods and taking large amounts of sedatives can lead to a thick and greasy coating.
(3) Influence of Oral Conditions on Tongue Appearance
Missing teeth can cause the tongue coating to be thicker on the same side, dentures can leave bite marks on the tongue edges, and mouth breathing during sleep can thicken the tongue coating. Clinical observations should be careful to distinguish these factors to avoid misdiagnosis.
Generally speaking, tongue quality reflects the organic changes of the body’s organs, while tongue coating often reflects functional changes. Changes in tongue quality occur more slowly, while changes in tongue coating occur more rapidly; however, both influence each other and should be observed together without bias. Additionally, continuously observing tongue color dynamically and focusing on before-and-after comparisons is also an important method in tongue diagnosis.
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