The tongue has a fixed length to what it can tell us. While it is an important part of diagnosis, it is as important, but not more important than any other diagnostic. The same can be said about a patient's bowel movements or menstrual cycle: we can only glean so much information per system.
The tongue, at first glance, shows the state of the patient's shen and stomach qi.
Color
There are four possible colors a tongue body can show: pale, pale-red, red and purple. Pale has two subsets that depend on either more information that the tongue is showing or other symptoms the patient is expressing.
If a tongue is pale without coating, this can signify blood deficiency. If a tongue is pale with a wet/watery coating, this can mean yang deficiency. For both of these scenarios, it is best to garner more symptoms from the patient to make sure the diagnosis is correct.
Pale-red or slightly red is considered normal. Red can be diagnosed as general heat in the body. Purple can mean there is blood stasis.
When it comes to color, it can not only affect the entire tongue body, but specific areas as well. When this is the case, we can take our general diagnoses and apply them to an organ. An example of this is when the edges of the tongue are pale and missing their coating; a diagnosis of liver-blood deficiency is likely. One other situation can arise in the form of raised, red papillae. These are seen as heat as well.
Coating
There are six possible coatings that can be found on a tongue: thin-white, thin-yellow, thick-white, thick-yellow, peeled, or unrooted. A thin-white coating that looks as if it is growing out of the tongue like grass is considered normal. The coating is a reflection of stomach qi, as it is created by steam vapor rising up the esophagus as the stomach rottens and ripens the food we eat.
Thin-yellow indicates heat. Thick-white is diagnosed as too much fluid, reading as dampness. Thick-yellow is a combination of dampness and heat, forming the diagnosis of damp-heat.
Peeled indicates a stomach yin deficiency, while unrooted is viewed as the tongue coating sitting atop the tongue, which could be peeled off easily. Unrooted is diagnosed as stomach qi deficiency – a precursor to stomach yin deficiency.
We should take the time to mention the geographic tongue: the tongue coating missing in random patches all over the tongue. While this is similar to when the coating is generally peeled, indicating a stomach qi and stomach yin deficiency, the cause is often liver qi stagnation. If a tongue coating is black, it is extreme heat, likely due to long-term use of pharmaceuticals.
Just as the body color can affect the tongue generally and in organ-specific areas, the tongue coating is viewed the same.
Cracking
Cracking all over is perceived as a general yin deficiency. Again, similar to color and coating, cracking can be in organ-specific areas. This is diagnosed as yin deficiency of that organ. While cracks can show up if there is an actual patient symptom, they are more likely to show a tendency toward an illness or pattern.
Shape
There are five possible shapes a tongue can show: normal, thin, thick, deviated or misshapen. A normal tongue has a distinct U-shape to it. A thin tongue can mean width or thickness, and it is important to teach patients to relax their tongue, as this can affect the diagnosis. A thin tongue indicates a general fluid (blood and/or yin) deficiency, and more signs and symptoms are required to confirm this diagnosis.
A thick tongue can mean width or thickness, and shows there is retention of fluid, such as dampness or phlegm. A deviated tongue is diagnosed as internal wind.
Finally, a misshapen tongue can mean a couple of different things, depending on the shape. A tongue that has teeth marks imprinted in its sides indicates the spleen is not holding firm, and the tongue has become so lax that it is resting against the teeth. A hammerhead-shaped tip or a forked tongue indicates either mental-illness or a leaning toward it. While more rare, shrinking and swelling can occur in organ-specific areas.
Take-Home Points
Tongue diagnosis is an important part of the whole that is Chinese medicine diagnosis. In using a four-step process, we ensure that no information is missed, and we also see the fixed amount of information available to us as clinicians. A stool with only one leg is always a wobbly stool, so it is best to acquire a few more legs through questioning and feeling the pulse.
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