Why is the tongue coating red in the middle and white on both sides?

Tongue diagnosis is one of the important indicators in traditional Chinese medicine diagnosis. From the perspective of traditional Chinese medicine theory, observing the tongue color can tell the nature of the disease and the strength of the body's vital energy; looking at the tongue coating can tell the depth of evil spirits and the survival of stomach qi; and examining its moisture and dryness can verify the changes in the six evil pathogens and the loss of body fluids.

Yang deficiency tongue

The tongue appearance of yang deficiency is very similar to that of blood deficiency. The difference is that people with yang deficiency have white tongue coating, the tongue quality is very light, the tongue is not red, and looks "old"; while the tongue appearance of blood deficiency is pale white and looks relatively tender.

For people with yang deficiency, when the degree of yang deficiency is mild, the body has heavier moisture, so there is more saliva on the tongue, which Chinese medicine calls "slippery tongue coating"; when the degree of yang deficiency is more serious, the body fluid cannot evaporate upward, and the mouth will become dry and the tongue will become dry.

Blood deficiency tongue

If the edges of the tongue are very light in color, it indicates a mild blood deficiency. If there is not much tongue coating, and you can see through the tongue coating that the tongue is very light in color, or even somewhat transparent, this is a typical case of blood deficiency.

Yin deficiency tongue

If a person does not have an external infection, but has thin or no tongue coating and the tongue is red, people with this tongue appearance can basically be determined to have a yin deficiency constitution. If the tongue coating is very thin or there is no tongue coating (atrophy), it is also a manifestation of Yin deficiency. Many people also have geographic tongue, which means that the tongue coating falls off inexplicably, revealing the red tongue texture. This tongue phenomenon is mostly caused by yin deficiency.

Elderly people are more prone to Yin deficiency because as they age, more body fluids are consumed, and by old age there is not much left, resulting in a Yin deficiency constitution. Judging from the tongue, the tongue of the elderly is very red, with many deep cracks on it, and the tongue feels uncomfortable when eating spicy food. These are all manifestations of Yin deficiency.

Most people transform from a Yin deficiency constitution to a blood deficiency constitution. Yin deficiency and blood deficiency affect, involve and develop each other. Severe Yin deficiency will lead to blood deficiency. There are also many people with blood deficiency constitution. Their tongue was originally pale, but for some unknown reason, their tongue gradually turned red. This shows that their blood deficiency constitution has transformed into Yin deficiency constitution.