Black moss on the tongue may be due to physiological factors, pigmentation caused by food or medication, etc. Pathological factors are mainly fungal infections. 1. Physiological factors: taking dark-colored foods or drinks that can adhere to the tongue, or using medications such as chlorhexidine mouthwash, etc., will cause the pigment to adhere to the tongue, resulting in a long black moss on the tongue. This is generally not necessary to pay attention to. 2. Pathological factors: the fungal infection that causes long black moss on the tongue is most common in the genus Trichoderma, Rhizopus niger, which produces melanin that colors the filamentous papillae black and makes the back of the tongue black and fluffy. Long black moss on the tongue may also have other pathological factors, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.