A white tongue may be a sign of poor oral cleansing or the presence of diseases of the tongue, such as hairy tongue and oral candidiasis. 1. Poor oral hygiene. When the diet bread or excessively greasy food, oral hygiene is not in place, which can lead to food residues and excessive tongue papilla keratinized layer retained on the back of the tongue, the appearance of the back of the tongue white. 2. Hairy tongue. When the oral environment is in poor condition, smoking or abuse of antibiotics and other reasons, there may be excessive elongation or delayed shedding of filiform papillae on the dorsum of the tongue, forming a hairy damage, most often seen in adults after the age of 30, with obvious bad breath. 3. Oral candidiasis. When the oral cavity is infected with Candida, a pseudomembrane as white as snow and the size of a needle tip can appear on the back of the tongue, which can be removed, and spores and hyphae can be seen under the microscope. The normal surface of the tongue has a thin and whitish layer of filamentous papillary keratinized layer, if suddenly thickened or accompanied by pain, it is recommended to go to the hospital in time for examination and treatment.