In clinical observation of the tongue, it is not sufficient to only examine the tongue quality or the tongue coating separately; both must be analyzed together to guide the differentiation of syndromes.
Generally speaking, changes in tongue quality occur relatively slowly, or it can be said that tongue quality is difficult to change in a short period of time.The tongue quality usually reflects overall, essential, and internal information, such as the strength or weakness of the constitution, whether the constitution is more cold or hot, the abundance or deficiency of Qi, blood, and body fluids, the strength of organ functions, and it can also reflect the nature of diseases and pathogens, the depth of pathogen invasion, and the progression or regression of the disease.
In contrast, changes in tongue coating occur relatively quickly; sometimes, there are significant changes in the morning, noon, evening, or before and after meals. Personally, I believe that the tongue coating mainly reflects the state of the spleen and stomach’s transformation and transportation, as well as the changes in body fluids and the existence of stomach Qi, reflecting relatively superficial and localized information. Of course, the tongue coating can also reflect the function of the spleen and stomach, the nature of pathogens, the location of diseases, the abundance or deficiency of body fluids, and the strength of righteous Qi. Due to the slow changes in tongue quality and the rapid changes in tongue coating, overall, the significance of observing tongue quality is clearer and greater than that of observing tongue coating.
In general, the changes in tongue quality and tongue coating areconsistent, and the information reflected is consistent. For example, in the case of interior excess heat syndrome, it often manifests as a red tongue quality, with a yellow coating that is relatively dry; in the case of interior deficiency cold syndrome, it often manifests as a pale tongue quality, with a white coating that is often moist. However, sometimes the information reflected by tongue quality and tongue coating is not consistent. For example, when pathogenic heat rapidly enters the Ying and blood levels, the tongue may be bright red, while the coating is white and dry, because the heat toxin quickly enters the Ying level and damages body fluids, leading to the tongue coating not yet turning yellow and already being dry; another example is a red tongue quality with a thick white coating resembling powder accumulation, which is also a manifestation of excessive pathogenic heat, and not caused by cold pathogens. A tongue coating that is gray-black and dry is often indicative of heat syndrome, while gray-black and moist is often indicative of cold syndrome. For instance, a tongue quality that is red or dark red, with a tongue coating that is white and slippery, indicates an exterior pathogen, with heat in the Ying level and dampness in the Qi level, while in the case of internal injury, it indicates yin deficiency with excessive fire combined with phlegm-damp food accumulation.
Therefore, during clinical examination, it is necessary to combine tongue quality and tongue coating for comprehensive analysis to gain a more complete and accurate understanding of the disease.
