The appearance of black spots on the side of the tongue is not necessarily cancerous, but may also be due to bruising, nevus pigmentosus, and hairy tongue factors. 1. Bruising: black spots on the side of the tongue may be caused by bruising, such as accidental bites, long-term use of anticoagulant drugs, etc., which may lead to the phenomenon. 2. Nevus pigmentosus: black spots on the side of the tongue may belong to nevus pigmentosus, which is formed by pigment cells in the oral cavity. However, nevus nigra has some malignant changes, so we need to be vigilant. 3. Hairy tongue: If the area of black spots on the side of the tongue is relatively large, it may be caused by the hairy tongue, which may appear black or dark brown. Black spots on the side of the tongue are not necessarily cancer, but may also be other diseases. No matter which factor, must go to the hospital in time to improve the examination, under the guidance of the doctor to take standardized treatment, not private treatment, so as not to lead to adverse consequences.