Tongue Diagnosis
Overview
Tongue diagnosis (舌诊, shé zhěn) is a fundamental diagnostic method in Traditional Chinese Medicine (TCM) that involves examining the tongue's appearance to assess a person's physical condition. According to Cao Bingzhang's "Guide to Tongue Diagnosis," "Examining the tongue body can determine the deficiency or excess of internal organs, while observing the tongue coating can assess the depth of pathogenic factors." When conducting tongue diagnosis, both the tongue body and tongue coating should be considered together. In most cases, they reflect pathological conditions consistently, but when they don't align, comprehensive analysis with consideration of other symptoms is necessary to make an accurate diagnosis.
History
The practice of tongue diagnosis has ancient roots in China. As early as the Shang Dynasty (1600-1046 BCE), oracle bones contained records of "diagnosing tongue diseases." The "Neijing" (Inner Canon of the Yellow Emperor), compiled between the 3rd and 5th centuries BCE, contains numerous references to tongue diagnosis, including the observation that yellow tongue coatings indicate internal heat. The "Lingshu·Jingmai" (Spiritual Pivot - Meridians) states: "The spleen meridian of Foot-Taiyin connects to the root of the tongue and spreads beneath it," and "The kidney meridian of Foot-Shaoyin borders the root of the tongue." These texts established the close connection between the tongue and internal organs, laying the foundation for TCM tongue diagnosis theory.
During the Han and Tang Dynasties, Zhang Zhongjing coined the term "tongue coating" and established tongue diagnosis as a basis for pattern identification and treatment. In his "Treatise on Cold Damage and Miscellaneous Diseases," Zhang skillfully applied tongue diagnosis to determine the nature, location, and progression of diseases, providing invaluable clinical experience for later physicians.
The earliest specialized work on tongue diagnosis was "Ao's Golden Mirror of Tongue Diagnosis for Cold Damage," also the world's first monograph on the subject. Written during the Yuan Dynasty (13th century) by someone with the surname Ao, it originally contained 12 tongue images, which were later expanded to 36 by Du Qingbi and published in 1341. During the Ming and Qing Dynasties, tongue diagnosis flourished, with numerous physicians conducting in-depth research and producing important academic works. These gradually spread to neighboring countries such as Japan, Korea, and Vietnam. In the Qing Dynasty, Zhang Deng's "Cold Damage Tongue Mirror" and "Tongue Differentiation" introduced new aspects of tongue diagnosis. In modern times, Cao Bingzhang compiled "Guide to Tongue Diagnosis," further enriching the field.
Since the 1980s, Zhang Boli has initiated research on the modernization of TCM, including the standardization of tongue diagnosis, opening new research directions in tongue chromatics and sublingual diagnosis. In 2021, the International Organization for Standardization (ISO) officially released the international standard "Traditional Chinese Medicine - Vocabulary for Diagnostics - Part 1: Tongue" (ISO 23961-1:2021), marking a significant milestone for the global recognition of TCM diagnostic methods.
Key Information
| Aspect | Description | Clinical Significance |
|---|---|---|
| Tongue Body | The muscular and vascular tissue of the tongue | Reflects the condition of internal organs, blood status, and body fluids |
| Tongue Coating | The layer covering the tongue surface, produced by stomach qi | Indicates the nature and severity of pathogenic factors |
| Normal Tongue | Soft, flexible, pale red body with thin, white, evenly distributed coating | Represents healthy physiological function |
| Color Changes | Pale, red, purple, etc. | Pale indicates deficiency; red suggests heat; purple may indicate blood stasis |
| Coating Changes | Thin, thick, white, yellow, etc. | White coating suggests cold; yellow indicates heat; thick coating suggests accumulation |
| Shape Changes | Cracked, enlarged, with teeth marks | Cracked tongue often indicates yin deficiency; enlarged tongue suggests spleen deficiency |
Cultural Significance
Tongue diagnosis holds significant cultural importance in TCM and East Asian medical traditions. It represents one of the "four examinations" (望闻问切, wàng wén wèn qiè) in TCM diagnostic methods, alongside observation, listening/smelling, and inquiry. This comprehensive diagnostic approach has been refined over millennia and remains central to TCM clinical practice.
The practice has influenced traditional medicine across East Asia, with adaptations in Japan (as "shinshin"), Korea, and Vietnam. The 2021 ISO standard for tongue diagnosis terminology (ISO 23961-1:2021) represents a significant step toward international recognition and standardization of TCM diagnostic methods, facilitating cross-cultural medical exchange.
Modern Status
In contemporary practice, tongue diagnosis continues to be a vital diagnostic tool in TCM. Modern research has focused on objectifying and standardizing tongue diagnosis through technological advancements. The TFDA-1 tongue diagnosis instrument, combining colorimetry and artificial intelligence technology, has obtained national Class II medical device certification in China. Similarly, AI-powered tongue diagnosis systems can identify 106 different constitutional states with accuracy rates exceeding 98%.
These technological innovations have expanded the applications of tongue diagnosis beyond traditional clinical settings. AI tongue diagnosis functions have been integrated into smart healthcare scenarios like "Harmony Hospital". International academic exchanges have also promoted tongue diagnosis globally, with educational content reaching over 27 million views on overseas platforms.
Despite technological advancements, traditional tongue diagnosis remains fundamental in TCM education and clinical practice. The 2021 ISO standard, developed by Professor Wang Yiqin's team from Shanghai University of Traditional Chinese Medicine, includes multilingual terminology and typical tongue images, playing an important role in the international standardization of TCM diagnostic terminology and the international trade of tongue diagnosis instruments.
References
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Maciocia, G. (2015). The Foundations of Chinese Medicine: A Comprehensive Text (3rd ed.). Elsevier Health Sciences.
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Wang, Y., Chen, J., Lu, W., et al. (2021). ISO 23961-1:2021 Traditional Chinese medicine - Vocabulary for diagnostics - Part 1: Tongue. International Organization for Standardization.
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Cao, B. (1923). Bian She Zhi Nan (Guide to Tongue Diagnosis). Reprinted by Shanghai Science and Technology Press, 1987.
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Lu, Y., & Zhang, D. (2018). Modern Research on Traditional Chinese Medicine Tongue Diagnosis. China Medical Science Press.
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Zhang, B. (2019). Innovation and Development of Traditional Chinese Medicine Diagnosis Technology. People's Medical Publishing House.