Research on Tongue Coating as of May 20, 2001

Research on Tongue Coating as of May 20, 2001

Typically, the tongue coating seen during clinical examination consists of keratinized papillae on the tongue surface and the desquamated cells distributed among them, along with a small amount of food residue and bacteria. The filiform papillae and their keratinized structures form the basic framework of the tongue coating. Filiform papillae cover about two-thirds of the front part of the tongue, and each is composed of primary and secondary papillae. The primary papilla resembles a crown, while the secondary papilla consists of several hair-like projections growing from the primary one. The primary papilla is covered by squamous epithelium, whereas the secondary papilla has plaque and tilts toward the pharynx. Both primary and secondary papillae are supported by columnar axes, which are connective tissue structures. The filiform papillae in different parts of the tongue are broadly similar, except that the number of secondary papillae varies greatly. This report was presented by Professor Liu Geng from Fudan University in Shanghai, but he did not conduct pathological research on tongue images, which is a limitation. Based on my 40 years of clinical experience, I propose the following conclusions—whether they are correct remains to be seen in future clinical practice.

1. Tongue body Represents the rise and fall of vital energy. Enlargement indicates blood stasis and edema—purple-red for the former, pale white for the latter; thinness suggests dehydration and malnutrition; pale color indicates blood deficiency and qi deficiency; red color signifies yin deficiency and excessive heat.

2. Tongue coating Represents the waxing and waning of pathogenic factors. Yellow indicates heat, which can correspond to inflammation and infection in modern medicine, showing that the filiform and secondary papillae, along with the hair-like projections, are filled with numerous polymorphonuclear leukocytes and inflammatory desquamated cells; white indicates cold, suggesting that the filling cells are mainly epithelial cells, indicating gastrointestinal dysfunction; thick coating means disease progression, thin coating means disease regression, and absence of coating indicates depletion of yin fluids—i.e., dehydration and electrolyte imbalance.