What causes mouth ulcers?

Mouth ulcers result from inflammation due to infections caused by bacteria, viruses and fungi. Infections of the skin around the mouth, mucous membranes inside the mouth, gums, and tongue are common causes of mouth ulcers.

Trauma that causes damage to lips, tongue, gums, and inside of mouth is also a common cause of mouth ulcers. Damage to the mouth can be the result of excessive teeth brushing, trauma, or dentures that are not fitted properly, each of which can cause inflammation, redness and ulcers. Mouth ulcers can also result from underlying conditions, such as a weakened immune system or hormonal changes.

Common causes of mouth ulcers

The most common causes of mouth ulcers are related to disturbances of the mouth and include:

  • Bacterial infections
  • Canker sores
  • Dietary deficiencies, such as lack of vitamin B-12, zinc, folate (folic acid), or iron
  • Emotional stress
  • Food allergies
  • Nutritional deficiency
  • Spicy foods
  • Substance abuse, especially methamphetamine use
  • Toothpastes and mouth rinses containing sodium lauryl sulfate
  • Viral infections

Other causes of mouth ulcers

Mouth ulcers can also have other causes including:

  • Behcet’s syndrome (a disease characterized by widespread inflammation of the blood vessels)
  • Candidiasis (a fungal infection)
  • Celiac disease (severe sensitivity to gluten from wheat and other grains that causes intestinal damage)
  • Crohn’s disease (inflammatory bowel disease that can affect any part of the intestine)
  • Herpes simplex virus
  • Human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS)
  • Immune system diseases, such as systemic lupus erythematosus (disorder in which the body attacks its own healthy cells and tissues)
  • Ulcerative colitis

Traumatic causes of mouth ulcers

Trauma to the mouth or gums may lead to mouth ulcers. Examples of traumatic causes include:

  • Abrasions
  • Cuts
  • Ill-fitting dentures or dental appliances

Serious or life-threatening causes of mouth ulcers

In some cases, mouth ulcers may be a symptom of a serious or life-threatening condition that should be evaluated immediately in an emergency setting. These include:

  • Immune system disorders
  • Oral cancers

Questions for diagnosing the cause of mouth ulcers

To diagnose your condition, your doctor or licensed health care practitioner will ask you several questions related to your mouth ulcers including:

  • When did you first notice ulcers in your mouth?
  • How often do you brush your teeth?
  • Do you have any other symptoms?
  • What medications are you taking?

What are the potential complications of mouth ulcers?

Because mouth ulcers can be due to serious diseases, failure to seek treatment can result in serious complications and permanent damage. Once the underlying cause is diagnosed, it is important for you to follow the treatment plan that you and your health care professional design specifically for you to reduce the risk of potential complications including:

  • Difficulty chewing food or swallowing liquids
  • Serious infections
  • Spread of cancer
  • Spread of infection
  • Tooth loss


  1. Canker sores. PubMed Health, a service of the NLM from the NIH. http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001993/.
  2. Cold sores. Medline Plus, a service of the National Library of Medicine National Institutes of Health. http://www.nlm.nih.gov/medlineplus/coldsores.html.
  3. Domino FJ (Ed.) Five Minute Clinical Consult. Philadelphia: Lippincott Williams & Wilkins, 2013.

What are mouth ulcers?

Ulcers in the mouth are a common symptom of infection, inflammation, trauma, malignancy, and other underlying conditions and diseases. Mouth ulcers result from pathogens, such as bacteria, viruses and fungi, which inflame the lining of the mouth, causing swelling, redness, and ulcer formation. Ulcers most commonly occur on the inside of the mouth but may also occur on the tongue and lips, or in... Read more about mouth ulcersintroduction


What other symptoms might occur with mouth ulcers?

Mouth ulcers may accompany other symptoms, which vary depending on the underlying disease, disorder or condition. Symptoms that frequently affect the mouth may also involve other body systems.

Symptoms that may occur along with mouth ulcers

Mouth ulcers may accompany other symptoms associated with an infection including:

Medical Reviewer: William C. Lloyd III, MD, FACS Last Annual Review Date: Sep 6, 2013 Copyright: © Copyright 2014 Health Grades, Inc. All rights reserved. May not be reproduced or reprinted without permission from Health Grades, Inc. Use of this information is governed by the HealthGrades User Agreement.

This Article is Filed Under: Mouth, Teeth and Oral Health