The dryness of the tongue at night while sleeping is related to environmental influences, reduced glandular secretion, and other reasons. Dryness of the tongue occurs because the nasal cavity is not open and breathing through the mouth is taken, and the repeated airflow takes away the moisture in the mouth as well as the moisture on the tongue. Decreased secretion of oral glands, mumps, parotid stones, obstruction of parotid ducts, parotid tumors, dryness syndrome, affect the secretion of glands, the tongue cannot be lubricated, and dryness of the tongue occurs. Local inflammation of the tongue surface, inflammation stimulation of the tongue dryness. Heavy sweating, dehydration of body water, insufficient blood volume, hemorrhage, hypertonic dehydration, repeated vomiting and diarrhea, causing dry mouth.