Tongue diagnosis: how Chinese medicine reads the tongue
Tongue diagnosis, she zhen, is the part of the looking examination in which the tongue body (she zhi) and its coating (she tai) are read as a map of the interior. The body's colour, shape, and moisture show the state of the qi, Blood, yin, and yang of the organs; the coating shows the state of the Stomach qi and the nature and depth of any pathogen. A healthy tongue is pale red, supple, neither swollen nor thin, moist, with a thin white coat that has root. Every departure is read against that: pale is deficiency or cold, red is heat, purple is stasis, a swollen and scalloped body is dampness and Spleen qi deficiency, a thin body is deficient Blood or yin, cracks are dryness and yin deficiency, a thick coat is a pathogen or an accumulation, a yellow coat is heat, a greasy coat is damp or phlegm, and a peeled, mirror-smooth tongue is Stomach yin exhausted. The Suwen ties the tongue to the Heart, which opens into it, and the mouth to the Spleen, so the tongue reports first on those two.
How to look
The tongue is read in daylight, in the morning, before food or drink that stains it and before it is brushed or scraped. It is put out without force for a few seconds and then withdrawn and put out again, because a tongue held out and strained darkens and misleads. Coffee, tea, and Huang Lian yellow the coat; blueberries and wine purple it; milk whitens it; a coat scraped that morning looks peeled. The order is body first, coating second: colour, then shape, then moisture and movement of the body; colour, thickness, moisture, texture, root, and distribution of the coat; and finally the veins beneath.
The map
The tip belongs to the Heart, with the Lung just behind it; the centre to the Spleen and Stomach; the root to the Kidney, the Bladder, and the Intestines; the two sides to the Liver and Gallbladder. A red tip is Heart fire or heat in the Heart from worry and poor sleep. Red sides are Liver heat. Teeth marks on the sides are the Spleen's weakness, since a swollen tongue presses against the teeth. A peeled centre is Stomach yin injured. A thick coat at the root alone is damp or heat lodged in the lower burner. The warm-disease school of Ye Tianshi read the tongue at each of the four levels of a fever, and much of the modern coating lore comes from that school.
The body
| Sign | What it shows |
|---|---|
| Pale | Deficiency of qi, Blood, or yang; cold |
| Pale, swollen, wet | Yang deficiency with damp |
| Red | Heat, excess if the coat is thick, deficiency if the coat is absent |
| Crimson, deep red | Heat at the nutritive or Blood level; severe yin deficiency |
| Purple, bluish | Cold with Blood stasis |
| Purple, reddish | Heat with Blood stasis |
| Swollen with teeth marks | Spleen qi deficiency, dampness |
| Thin and small | Blood deficiency if pale, yin deficiency if red |
| Cracked | Yin deficiency, heat drying the fluids; lifelong cracks are constitutional |
| Red prickles, raised papillae | Heat in the organ of that region |
| Stiff or deviated | Internal wind, phlegm obstructing, wind-stroke |
| Trembling | Qi and Blood deficiency, or Liver wind |
| Dark, distended veins beneath | Blood stasis |
The coating
The coating is the Stomach's qi rising as a fine moist film. Thin means the pathogen is at the surface or the disorder mild; thick means it is in the interior or an accumulation of food, damp, or phlegm has formed; a coat that grows thicker over days is a pathogen going deeper and one that thins is a pathogen leaving. White is cold or the exterior; yellow is heat, and the deeper the yellow the deeper the heat; grey and black are extremes of either, told apart by moisture, dry and black being fire and wet and black being cold. Dry means the fluids are injured; wet and slippery means damp or yang deficiency. Greasy (ni), a fine sticky film that does not scrape off, is damp or phlegm; curd-like (fu), coarse like tofu dregs and easily scraped, is heat with turbid food stagnation. A coat with root grows from the tongue and shows the Stomach qi intact; a rootless coat sits on it like a scattering and shows the Stomach qi weak. A peeled patch is yin deficiency in that region; a whole mirror tongue is Stomach yin and Kidney yin exhausted.
In the texts and in practice
The Ao Shi Shang Han Jin Jing Lu of the Yuan dynasty is the first monograph on the tongue, written for cold-damage fevers, and the warm-disease physicians extended it; the modern colleges teach from colour atlases that follow the same categories. The tongue is read against the pulse, and the two correct each other: a wiry pulse with a normal tongue is qi stagnation, with red sides it is Liver heat, with a pale body it is Blood deficiency. The tongue changes more slowly than the pulse and is the more honest witness.