What causes black tongue coating?

In TCM, four syndromes are needed to differentiate diseases. Observation is to observe with naked eyes. Tongue coating needs to be distinguished by observation. Tongue coating can accurately reflect the specific conditions of yin and yang imbalance in the human body. Normally, tongue coating is composed of exfoliated keratinocytes, bacterial food debris, oozing white blood cells, saliva, etc. Black tongue coating TCM angle generally consider the body heat deficiency, the body is relatively dry, but also can be a state of yang deficiency yin cold. This situation requires oral anti-fire drug treatment. Usually pay attention to eat more digestible food, eat more fresh fruits and vegetables, moderate exercise to promote the recovery of organ function.