Oral ulcers are painful sores anywhere in the mouth. The most common are aphthous mouth ulcers, which affect at least 1 in 5 people at some point in their lives. Minor aphthous mouth ulcers are usually <10mm in diameter, not very painful, and will resolve spontaneously in 7-10 days without leaving a scar. Major aphthous mouth ulcers tend to be larger than 10mm in diameter, last from 2 weeks to months, and can be very painful and cause difficulty in eating. Oral ulcers are not infectious, but may be related to other factors, including:

• Smoking cessation
• Local trauma to the mucosa in the mouth e.g. ill-fitting dentures
• Positive family history of oral ulcers
• Vitamin or mineral deficiency (vitamin B12, folate and iron)
• Hormonal changes (notably in premenstrual period)
• Exposure to an allergen
• Anxiety
• Drug treatment e.g. methotrexate, NSAIDs, bisphosphonates, nicorandil, propylthiouracil (used to treat hyperthyroidism). Also recreational use of cocaine.
• Conditions such as coeliac disease and chronic kidney disease.

Infective causes include herpes simplex viruses, human herpesvirus 8 (HHV-8, associated with Karposi’s sarcoma of the gingiva), Candida albicans, coxsackievirus A, Epstein-Barr virus, cytomegalovirus, tuberculosis and secondary syphilis.  

Mouth ulcers may be malignant: squamous cell carcinoma is the most common oral cancer, and may present as a slow-growing, painless, ulcer on the side of the tongue, floor of the mouth or soft palate. The main avoidable risk factor is tobacco smoking.

Radiation therapy can also cause acutely painful mouth ulcers, but these usually resolve when therapy ends.

Treatment depends on severity and underlying cause, but a warm saline mouthwash can aid healing and relieve discomfort. Corticosteroids and local or systemic analgesics may also be indicated.   Consider referral (2-week wait) if unexplained ulceration in the oral cavity persists >3 weeks