Black spots on the tongue are the precursor or manifestation of many diseases, such as mucosal black spots, hyperpigmented polyp syndrome, pigmented nevi, chronic hypoadrenocorticism and so on. 1. Mucosal black spots: black spots on the tongue may belong to mucosal black spots, which can appear on the tongue and other mucous membranes of the oral cavity, with a clearer border, not higher than the surface of the mucous membranes, and not affecting the function of the tongue. 2. Hyperpigmented polyp syndrome: Hyperpigmented polyp syndrome can show hyperpigmentation of the oral mucosa and tongue mucosa, which can lead to the phenomenon of black dots on the tongue, and can be accompanied by multiple polyps in gastrointestinal tract. 3. Pigmented nevus: black spots on the tongue may also belong to pigmented nevus, which can also occur on the tongue, similar to the appearance of pigmented nevus on the skin. 4. Chronic hypoadrenocorticism: this disease can also cause the phenomenon of black spots on the tongue, which is a relatively rare disease. There are many reasons for black spots on the tongue, and it is recommended to consult a doctor in time after the symptoms appear, and give standardized treatment after a clear diagnosis, so do not ignore the symptoms and take them lightly.