Color of the coating can be generally divided into white, yellow, gray and black or a mixed variety.  Observation of coating color can yield valuable understanding of the disease.

(1)        White coating:  this usually indicates exterior syndrome and cold syndrome.  As the external pathogen has not entered internal section of the body, the coating remains unchanged with the normal white coating.  If the tongue appears pale, with white coating and rather wet, this usually indicates interior cold, or damp cold.  However, in exceptional cases, white coating may also indicate heat.  For instance, if the tongue is full of white “powdery fur” that does not appear dry when examined.  This is probably due to excessive noxious interior heat stimulated by exogenous turbid pathogenic force.  This is commonly seen in infectious epidemic disease, or carbuncle.  It is also possible that the white coating may appear like coarse sand known as “white-sand coating” or “rough and gapping fur”.  This is due to quick transformation of dampness into heat impairing body fluid.  The internal heat rapidly becomes burning hot before the white-colored fur could turn yellowish.  This is common in the case of patient wrongly given tonic herbs.