Black tongue may be due to pigmentation, poor oral hygiene and black hairy tongue. 1. Pigmentation: Consumption of some darkly pigmented food, such as coffee, chocolate, etc., may lead to the blackening of the back of the tongue, which can be relieved after general cleaning. 2. Poor oral hygiene: For some patients with poor oral hygiene, especially when brushing teeth without cleaning the back of the tongue, it is easy to cause the accumulation of food debris, resulting in the appearance of tongue moss, some patients will appear black. It is necessary to maintain oral hygiene and adopt the correct way of brushing teeth. 3. Black hairy tongue: it is caused by excessive elongation and delayed shedding of filiform papillae, which is related to smoking and poor oral hygiene. It is recommended to maintain oral hygiene, trimming or use of containing drug mycotoxin tablets treatment, quit smoking and alcohol. It is recommended to go to the regular hospital stomatology consultation, by the physician examination after a clear diagnosis, symptomatic treatment.