Blood blisters inside the mouth are usually not a precursor of cancer, but are mostly caused by inadvertent damage to the oral cavity when eating. When blood blisters appear in the mouth, the first thing to consider is to bite the oral mucosa inadvertently when eating, or eat food that is too hot or too hard, resulting in damage to the oral mucosa. Such blood blisters can be large or small, and relatively small blood blisters can be naturally absorbed and healed, while larger blood blisters with obvious foreign body sensation can be punctured with a clean, sterile syringe to draw out the stasis. Blood blisters may also be caused by vascular malformations forming hemangiomas, which can be improved by surgical removal or local sclerotherapy. Blood blisters in the mouth will not be directly considered as cancer. If there is a symptom of blood blisters inside the mouth, patients are advised to chew slowly and not to be too hasty in their usual diet, and also to avoid eating too hot or hard food to avoid damaging the mucous membrane.