There can be many causes for mouth blisters or sores, including different types of infections, a burn or injury, braces or dentures that do not fit properly, stress, mouth cancer and some medical conditions, according to the National Institutes of Health's MedlinePlus. Mouth infections can be caused by a virus or bacteria. For example, fever blisters and hand, foot and mouth disease are caused by viral infections.
Trauma is the most common cause of mouth blisters, states HealthGuidance. The injury usually results from biting the inside of the lips or cheeks while eating, by accident or as a nervous reaction. This type of blister usually heals on its own after a few days. If it persists, HealthGuidance suggests chewing basil leaves or applying basil paste to the blister three times daily.
Herpes simplex virus type 1 causes more than 95 percent of recurring fever blister outbreaks, states the National Institute of Dental and Craniofacial Research in a paper published by Publications.USA.gov. The virus is contagious, often spread by kissing. Blisters appear in the mouth three to five days after infection. General aches, fever and swollen neck glands accompany the fluid-filled blisters. Blisters often merge and form a yellowish crust over the resulting mouth sores.
Certain foods can burn the mouth, leading to the formation of blisters. A disease like mouth cancer can also present symptoms of blister or sores inside of the mouth. Similarly, cancer treatments, such as radiation and chemotherapy drugs, can also lead to mouth blisters or sores, reports Merck Manuals.
Mouth sores can also be symptoms associated with many different diseases or medical conditions, such as AIDS, autoimmune disorders, syphilis and bullous pemphigoid, states the Merck Manuals. Other causes can be the use of chewing tobacco and a vitamin deficiency.
When there are other symptoms, such as a fever or a rash that present with mouth blisters, people should see a doctor. However, most mouth sores that are not related to an illness or disease will resolve within one to two weeks, informs MedlinePlus. Some home treatments for mouth blisters are to use a pain reliever for mouth pain and avoid any type of food that may aggravate the problem like citrus fruits or spicy foods.