Mouth Ulcers — Causes, Types, Diagnosis & Treatment Guide — Symptoms, Causes & Treatment | MyMedicPlus

Mouth ulcers (oral ulcers or aphthous ulcers) are painful breaks in the oral mucosa — the lining of the mouth, lips, cheeks, tongue, and palate. They are extremely common: recurrent aphthous stomatitis (RAS), the most frequent cause, affects approximately 20% of the general population, making it the most common oral mucosal disease worldwide. Most mouth ulcers are benign, self-limiting, and resolve within 7-14 days without treatment. However, ulcers that are persistent (lasting more than 3 weeks), enlarging, painless, or associated with systemic symptoms must be investigated to exclude serious conditions including oral cancer, systemic inflammatory diseases (Behcet's disease, Crohn's disease, coeliac disease), haematological disorders, and viral infections (herpes simplex). Correct classification of the ulcer type guides appropriate management and avoids delayed diagnosis of serious underlying conditions.

Aphthous stomatitis (most common): the exact cause is unknown but involves T-cell-mediated mucosal damage in genetically susceptible individuals. Triggers include: minor trauma (biting the cheek, sharp tooth, new dental appliance), stress and anxiety, hormonal changes (menstrual cycle — some women have predictable perimenstrual ulcer flares), nutritional deficiencies (iron, vitamin B12, folate — particularly associated with recurrent major aphthous ulcers), sodium lauryl sulphate in toothpaste (irritant), and food sensitivities (gluten in coeliac, some report dairy or nuts as triggers). Systemic disease associations: coeliac disease (screen for anti-TTG IgA), Crohn's disease (aphthous-like ulcers in the mouth may precede GI symptoms), Behcet's disease (recurrent oral ulcers as a diagnostic criterion plus genital ulcers and eye disease), HIV and immunosuppression (atypical large, persistent ulcers). Herpes simplex virus (HSV-1): primary herpetic gingivostomatitis (children and young adults) — multiple vesicles breaking into ulcers on gingiva, palate, and tongue with fever and lymphadenopathy; recurrent herpes labialis ('cold sores') on lips. Traumatic ulcers: from denture trauma, sharp food, accidental biting.

Minor aphthous ulcers (most common, 80%): small (below 1 cm), round or oval, with a yellow-grey fibrinous base and erythematous halo; occur singly or in crops of 2-6; located on non-keratinised mucosa (buccal mucosa, labial mucosa, floor of mouth, ventral tongue, soft palate); heal within 7-14 days without scarring; mildly painful. Major aphthous ulcers (10%): larger (above 1 cm), deeper, more painful, often persisting for 2-6 weeks; may leave scarring; commonly affect the soft palate and tonsillar area. Herpetiform aphthous ulcers (10%): multiple tiny (1-2 mm) ulcers appearing in crops of 10-100, coalescing; not caused by herpes virus despite the name; extremely painful. Symptoms of herpes simplex: vesicular rash progressing to ulcers, fever, malaise, bilateral submandibular lymphadenopathy, pain with eating and swallowing, and drooling in primary infection. Behcet's disease oral ulcers: indistinguishable from major aphthous ulcers but in the context of genital ulcers, uveitis, and skin lesions.

Most mouth ulcers are diagnosed clinically based on their appearance, history, and response to treatment. However, persistent ulcers (lasting more than 3 weeks) require investigation and biopsy to exclude malignancy. Blood tests for recurrent aphthous ulcers: FBC (anaemia, macrocytosis — B12/folate deficiency), serum iron and ferritin, vitamin B12 and folate, coeliac antibodies (anti-TTG IgA with IgA level — screen for coeliac disease), HIV test in immunosuppressed patients. Viral tests: HSV swab (PCR) for vesicular/ulcerative lesions — particularly if fever is present. Pathergy test and HLA-B51 testing for suspected Behcet's disease. Biopsy: any oral ulcer persisting beyond 3 weeks, or showing features suspicious for malignancy (indurated/hard edge, irregular border, non-tender, on the lateral tongue or floor of mouth, fixed to underlying tissue, in a tobacco/alcohol user) — requires urgent referral for biopsy and histopathological examination. Oral cancer is the most important condition to exclude in persistent ulcers.

Minor aphthous ulcers often require only symptomatic relief while awaiting self-resolution. Topical analgesics: benzydamine hydrochloride (Difflam) mouthwash and spray provides local anaesthesia and anti-inflammatory effect; lidocaine gel or paste for immediate pain relief before meals. Topical corticosteroids: triamcinolone acetonide in orobase (Adcortyl in Orabase), betamethasone sodium phosphate 0.5 mg in 10 mL water mouthwash — reduce inflammation and promote healing when applied at the first sign of ulceration. Cauterisation: trichloroacetic acid applied by a dentist or doctor provides immediate pain relief by chemical debridement — effective for individual persistent ulcers. Mouthwash: chlorhexidine gluconate reduces secondary bacterial infection and may reduce duration and pain. Systemic corticosteroids: short course prednisolone for severe major aphthous disease or Behcet's disease oral ulcers. Colchicine or thalidomide: for severe recurrent major aphthous disease unresponsive to topical therapy. Herpes simplex: oral aciclovir 200 mg 5x daily for 5 days reduces duration and severity in primary infection; valaciclovir for recurrent labial herpes. Treat underlying systemic cause (coeliac disease — gluten-free diet; B12 deficiency — replacement therapy). Iron and B12 supplementation reduces recurrence frequency when deficiencies are identified.

Persistent or extensive mouth ulcers can lead to secondary bacterial infection, occasionally requiring antibiotic treatment. Severe major aphthous ulcers (greater than 1 cm in diameter) may cause significant functional impairment — difficulty eating, swallowing, and maintaining adequate nutrition and hydration, particularly in children with herpetiform or major aphthous disease. Recurrent aphthous stomatitis causing frequent, prolonged ulcers significantly impairs quality of life and may contribute to nutritional deficiency if eating avoidance becomes sustained. The most serious complication associated with a non-healing mouth ulcer is delayed diagnosis of oral squamous cell carcinoma — any ulcer persisting beyond 3 weeks has a meaningful risk of malignancy that rises with tobacco use, alcohol consumption, HPV-16 infection, and age over 40. Early-stage oral cancer has a cure rate above 80%, whereas advanced disease carries a 5-year survival below 50%. Behcet's disease, if unrecognised and untreated, can progress to uveitis with risk of blindness, neurological involvement (neuro-Behcet's), and life-threatening vascular complications including arterial aneurysms. In immunocompromised patients (HIV, organ transplant recipients, haematological malignancies), herpes simplex reactivation can cause extensive painful oral ulceration and rarely disseminate systemically causing herpes encephalitis — a medical emergency with significant mortality.

Avoid known personal triggers: keep a diary of ulcer onset and relation to food, stress, hormonal cycle, and activities. Switch to sodium lauryl sulphate (SLS)-free toothpaste — multiple studies show RAS frequency reduction. Avoid toothpaste with SLS (common ingredient in standard toothpastes — Biotene, Sensodyne Original are SLS-free). Soft toothbrush technique reduces mucosal trauma. Address nutritional deficiencies with dietary improvement or supplementation (iron, B12, folate). Use dental wax to cover sharp tooth edges or new orthodontic brackets. Stress management (mindfulness, exercise) may reduce stress-triggered flares. Avoid suspected dietary triggers. Ensure well-fitting dentures — dental review if poorly fitting. Topical steroids applied at the prodromal tingling phase of known recurrences may prevent full ulceration.

See a dentist or doctor promptly — and urgently if possible — for any mouth ulcer lasting more than 3 weeks without healing, as oral cancer must be excluded (oral cancer is most effectively treated when detected early). Urgent referral is required for ulcers that are painless, enlarging, have indurated or raised edges, are fixed to underlying tissue, or occur on the lateral tongue or floor of mouth in a tobacco or alcohol user. Seek same-week GP assessment for ulcers associated with genital ulcers or eye inflammation (possible Behcet's disease), large or extremely painful ulcers impairing eating or swallowing, or ulcers in the context of HIV infection or immunosuppression. Children with a first episode of very painful widespread oral ulcers with fever need prompt paediatric/GP assessment for primary herpetic gingivostomatitis — antiviral treatment reduces severity.