We’ve already looked at how to interpret tongue shape and tongue color. Next in the tongue diagnosis series…how to interpret tongue coat! Tongue coat is another important feature used to read the tongue. It can indicate more acute issues than tongue body color and shape because the coat changes relatively more quickly—though some aspects of tongue coat, such as gray coloration, can indicate a long-term disease process (1).
So, the coat’s thickness, color, texture, and location all tell us something. Also, whether the coat looks rooted to the tongue, like grass in a lawn (as it should), or appears to be floating on top has meaning. A normal tongue coat should be thin and white, resembling a “light dusting of snow.” Let’s just stick to some basics on color and thickness to get you started!
Why is there a coat on the tongue at all? The tongue coat is a byproduct of digestion and, as such, is an important indicator of digestive function, a large part of which is carried out by the Stomach and Spleen in Chinese theory. Tongue coat also reflects the status of other Organ systems in the body, such as the Lungs, Kidneys, and Liver, with the distribution of the coat on the tongue pointing towards where in the body a problem is. We’ll get into which Organ systems map to what parts of the tongue next time. And, as a reminder, Organ systems in Chinese medicine are capitalized to distinguish them from the Western medical ideas on organs. They don’t always overlap…
Tongue coat is also a handy way to determine if a problem in the body is due to heat, cold, dryness, or dampness, some pathogenic factors recognized in Chinese medicine. The coat can also indicate the intensity of a problem and whether it came from an outside factor invading the body (the flu, for example) or to an issue originating within the body (1).
Tongue Coat Color
The tongue coat can be different colors, or even mixes of colors, but I’m sticking to the very basics here…white and yellow.
A thin white coat is normal. Not clumpy like cottage cheese. Not greasy-looking. Not chalky and dry. A thicker white coat indicates coldness. For example, too much ice cream will quench the digestive fire. Ice cream also creates dampness, so the result will be a thick, white tongue coat (more on thickness in a moment).
A yellow coat indicates heat. For instance, too much stomach acid is a condition of excess heat that will show in a yellow coat (1, 2). The tongue coat may even be gray or black, either of which indicate a long-standing imbalance in the body (1).
Thin or Absent Tongue Coat
Since the coat is a byproduct of digestion, a very thin coat may indicate a deficiency in digestive function. For example, if the Stomach lacks the energy (qi) to do its job, the tongue will show a very thin coat, and what’s there may look like it’s floating on top of the tongue rather than rooted to it (1). Some support for when Stomach function is weak include nutrient-dense but easily broken-down foods like soups, Slippery Elm (organically grown only), well-cooked oatmeal, and rice congee or kitcharee.
Sometimes there isn’t a coat at all—for example, when the Stomach lacks fluids (yin deficiency). In this case, the tongue body itself will either be normal colored or, in more advanced cases, red (1). The tongue may even appear as if the coating has been peeled off, which looks painful—like scalding—but actually isn’t. In these cases, the problem may arise from irregular eating habits, rushing meals, not focusing on other things while eating and even from eating too many drying foods (3). Another instance where there may be no tongue coat is in Blood deficiency. In this case, the tongue body will be pale colored (1). Some supportive foods for the Stomach include cabbage, chickpeas, peas, tomatoes, millet, shiitake, and small amounts of beef (4). From a Western herbal standpoint, small amounts of digestive bitters taken before meals are helpful for stimulating digestive secretions. You can also refer here and here to the previous articles in this series for some supportive foods to eat for yin and Blood deficiency.
Thick Tongue Coat
A coating is considered thick if you can’t see the tongue body through it. This indicates an “excess” condition. For example, going back to the ice cream example, too much dairy leads to too much coldness and dampness and is reflected in a thick, white coat. These folks need some more foods that are warming or drying. Some examples include garlic, ginger, aduki beans, turnips, asparagus, pumpkin, amaranth, and celery (4).
In another example, food that is sitting around stagnating in the digestive tract results in heat and dampness, showing as a thick, greasy-looking, yellow tongue coat. This is called, simply enough, “damp heat.” Excess alcohol can also cause a thick, yellow coat. Mung beans are a food used to clear “damp heat,” as are amaranth, millet, cabbage, celery, cucumbers, mushrooms, spinach, small amounts of seaweed (4).
Now to really blow your mind: excess can come from deficiency (and vice versa). For example, too much heat (excess) will eventually dry up fluids/yin (deficiency). This may start out as a normal-colored tongue with a dry yellow coat, then progress to a red tongue with no coat at all.
It’s fun to check out your tongue coat throughout the day! Just be aware that many things impact its appearance. Smoking, for instance, results in a yellow coat. Antibiotics may result in bald spots or “peeling” of the coat. Artificial food coloring may give your tongue coat an interesting hue. Even eating a tuna melt…I once had a client come in right after eating this and his tongue coat was orange!
This article isn’t meant to be comprehensive…it’s just to give you a taste of what your tongue coat can tell you. Many other aspects of tongue coat are analyzed and can (and do!) fill multiple chapters in a book. For folks who want to go deeper, refer to any and all of the references below. Come back next time for mapping the regions of the tongue!
- Maciocia, G (1995) Tongue diagnosis in Chinese medicine. Revised Edition. Eastland Press, Seattle, WA
- Beinfield, H & E Korngold (1991) Between heaven and earth: A guide to Chinese medicine. Ballantine Books, NY.
- Pitchford, P (2002) Healing with whole foods. Asian traditions and modern nutrition. 3rd Ed. North Atlantic Books, Berkeley, CA.