What causes mouth ulcers?

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From the Guidelines

Mouth ulcers are typically caused by a combination of local and systemic factors, including minor injuries, immune system reactions, and underlying health conditions, as well as traumatic, infectious, allergic factors, and may be associated with skin disease, autoimmune disease, tumor, inflammatory bowel disease, and other conditions. The causes of mouth ulcers can be diverse and complex, and may involve local stimuli such as mechanical, physical, or chemical factors, as well as systemic causes such as nutritional deficiencies, hormonal changes, and food sensitivities 1. Some people may develop mouth ulcers due to viral infections like herpes simplex, or as a symptom of conditions such as Crohn's disease, celiac disease, or Behçet's disease 1. Certain medications, including NSAIDs and some antibiotics, may also cause mouth ulcers as a side effect.

Some key factors that may contribute to mouth ulcer formation include:

  • Minor injuries to the mouth tissue, such as accidentally biting your cheek or tongue
  • Immune system reactions, such as those caused by viral infections or autoimmune diseases
  • Underlying health conditions, such as Crohn's disease, celiac disease, or Behçet's disease
  • Nutritional deficiencies, particularly vitamin B12, iron, and folate
  • Hormonal changes and food sensitivities
  • Certain medications, including NSAIDs and some antibiotics

According to the most recent and highest quality study, the diagnosis and treatment of mouth ulcers should involve a comprehensive approach, including detailed clinical medical history inquiry, histopathological examination, and screening for underlying systemic diseases 1. This approach can help to improve diagnostic efficiency and avoid misdiagnosis or missed diagnosis. In some cases, further examinations such as blood tests, imaging studies, or biopsies may be necessary to determine the underlying cause of the mouth ulcer 1.

From the Research

Causes of Mouth Ulcers

The causes of mouth ulcers can be varied and complex. Some of the possible causes include:

  • Local trauma and stress 2
  • Systemic diseases and nutritional deficiencies, such as deficiencies in vitamin B1, B2, and B6 3 and vitamin B12 4
  • Food allergies and genetic predisposition 2
  • Immune disorders, such as HIV infection 2, 5
  • The use of certain medications 2
  • Gastro-intestinal diseases, such as celiac disease and inflammatory bowel diseases 5

Classification of Oral Ulcers

Oral ulcers can be classified into three main groups:

  • Acute ulcers with abrupt onset and short duration, which can be caused by trauma, bacterial infections, deep fungal infection, gastro-intestinal or systemic diseases 6, 5
  • Recurrent ulcers, which can be caused by postherpetic erythema multiforme or recurrent aphthous stomatitis (RAS) 5
  • Chronic ulcers with slow onset and insidious progression, which can be caused by drug-induced reactions, benign or malignant tumors, or other conditions 6, 5

Nutritional Deficiencies

Nutritional deficiencies, such as deficiencies in vitamin B1, B2, and B6 3 and vitamin B12 4, can contribute to the development of mouth ulcers. Replacement therapy with these vitamins can lead to significant clinical improvement in patients with recurrent mouth ulcers 3.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Treatment strategies for recurrent oral aphthous ulcers.

American journal of health-system pharmacy : AJHP : official journal of the American Society of Health-System Pharmacists, 2001

Research

Recurrent aphthous ulceration: vitamin B1, B2 and B6 status and response to replacement therapy.

Journal of oral pathology & medicine : official publication of the International Association of Oral Pathologists and the American Academy of Oral Pathology, 1991

Research

Aphthous ulcers and vitamin B12 deficiency.

The Netherlands journal of medicine, 1998

Research

[Aphthous ulcers and oral ulcerations].

Presse medicale (Paris, France : 1983), 2016

Research

Diagnosis of oral ulcers.

The Mount Sinai journal of medicine, New York, 1998

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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