Blood blisters on the tongue may be caused by traumatic blood blisters, vascular malformations, mucosal aspergillosis and other diseases, as follows. 1. Traumatic blood blisters: the tongue can be bitten by teeth or food burns, abrasions and other blood blisters, at first the blisters are bright red, and then become black, the blood blisters burst after the emergence of bright red trauma. 2. venous malformation: venous malformation can occur in the tongue, superficial lesions are blue or purple, can be mistaken for blood blisters, the lesion border is not clear, soft to touch, can be compressed, when the head is lower than the level of the heart, the lesion area can be congested and inflated. 3. Mucosal pemphigus: autoimmune herpetic disease, oral mucosa can be repeated blisters, blister fluid clear or blood blisters. Tongue blood blisters may have other reasons, it is recommended to go to the hospital in time, clear cause for targeted treatment.