Sudden black blood blisters on the tongue may be caused by traumatic blood blisters as follows. 1. often caused by eating too hot food, chewing large pieces of dry and hard food or swallowing too fast leading to oral mucosa abrasion, or due to external contusion, dental bite, sharp tooth tip, bad restorations and other scratches, causing traumatic blood blister. 2. larger blood blisters, often caused by swallowing too fast abrasion, up to 20~30mm. blood blisters can be rapidly expanded, pain symptoms are not obvious, there may be a foreign body sensation. At the beginning of the blister liquid bright red, and then become purple-black, after the rupture can form a bright red trauma, at this time the pain is obvious. There may be other reasons for the sudden appearance of black blood blisters on the tongue, it is recommended to go to the hospital in a timely manner, to clarify the cause of the disease and early targeted treatment.