Moistening and dryness of tongue fur: The tongue fur that is moist with moderate dampness is called moist tongue fur. The tongue fur with excessive dampness and slipperiness is called slippery tongue fur. The tongue fur that is dry, without fluid or even fissured is called dry tongue fur. The tongue fur that is dry, rough and sandy is called rough tongue fur.
The moistening and dryness of the tongue fur reflect the conditions and distribution of body fluid. Moist tongue fur indicates sufficiency and upward distribution of body fluid. Slippery tongue fur indicates cold-dampness, or re- tention of fluid and internal invasion of cold-dampness, or asthenia of yangqi and failure of qi to transform fluid. Dry and rough tongue fur indicates consumption of fluid by exuberant heat or consumption of yin fluid. The drier and rougher the tongue fur, the severer the consumption of body fluid. Such a condition is usually seen at the medium and advanced stages of exogenous febrile diseases. Besides, internal stagnation of pathogenic dampness, obstruction of yangqi or asthenia of yangqi and failure of qi to transform fluid may also lead to dry tongue fur, the manifestation of which is light-whitish tongue accompanied by chest oppression and dry mouth without desire to drink. ,
During the course of a disease, the change of the tongue fur from moisture to dryness indicates consumption of body fluid and severity of heat,while the change of tongue fur from dryness to moisture suggests abatement of pathogenic heat and gradual restoration of body fluid.