The main symptom is the appearance of large, dense blisters on the mucous membranes of the mouth, including the tongue or throat, which are as small as a pinhead and have thin walls that break easily, leaving a large, red, bleeding, ulcerated mucosal surface once the blisters have broken. Blisters on the tongue may also be due to traumatic blisters or even blood blisters caused by misaligned tooth tips or very sharp tooth tips or poor restorations that always bite or scratch the tongue mucosa, which should be corrected in time to prevent re-trauma to the tongue.