Black gums may be oral black spot, oral mucosa exogenous pigmentation and other diseases, specific as follows. 1. Oral black spot: a small, flat black or brown color change on the surface of the oral mucosa, caused by an increase in melanin deposition in the local mucosa, which can be seen in any part of the mucosa, gingiva, hard palate, buccal mucosa is common, usually single, the patient does not have any obvious self-conscious symptoms. 2. Exogenous pigmentation of oral mucosa: generally planted into the oral mucosa by external colored substances, the most common for amalgam pigmentation. Most commonly seen in the gingival mucosa adjacent to the filling body, can be black, gray, clear or irregular boundaries. Black gums may have other reasons, it is recommended to go to the hospital in time, clear cause for targeted treatment.