Black nevus-like dots on the inside of the mouth may be a normal phenomenon, or it may be caused by trauma, thrombocytopenic purpura and other factors. 1. Normal phenomenon: If it is congenital, there are black dots like nevus on the inner wall of the mouth after birth, it may be pigmented nevus, or birthmark, etc. These cases are usually normal, don’t worry too much. 2. Trauma: If you are hit by hard objects or eat hard food, you may damage the capillaries under the oral mucosa, which may lead to the appearance of small black blood blisters on the inner wall of the mouth. 3. Thrombocytopenic purpura: common symptoms for the skin, nasal cavity, oral mucosa and other parts of the bleeding spots, usually multiple intensive blood blisters, this situation is relatively rare compared to the blood blisters caused by trauma. After excluding the normal phenomenon, if the inner wall of the mouth often appears black like a mole of round spots, you should consult the doctor in time, active treatment, so as not to delay the condition.