What should I do about a mouth sore that has lasted for 1 month?

Urgent Evaluation Required: A Mouth Sore Lasting 1 Month Needs Biopsy

Any oral ulcer persisting beyond 2 weeks requires biopsy to exclude malignancy, and at 1 month duration, this is mandatory. 1, 2

Immediate Action Steps

Schedule a biopsy within the next week. The 2022 International Journal of Oral Science expert consensus guideline emphasizes that ulcers lasting this long can represent serious conditions including squamous cell carcinoma, lymphoma, tuberculosis, fungal infections, or systemic diseases like Crohn's disease. 1

Before the Biopsy: Essential Documentation

Document these specific characteristics now:

• Exact size in millimeters (measure with a ruler if possible) 2
• Precise location (which surface of the mouth—tongue, cheek, palate, gums) 3, 2
• Appearance: color of the base (yellow-white pseudomembrane suggests infection or inflammation), border characteristics (well-demarcated vs irregular), and surrounding tissue inflammation 1, 3
• Pain level on a 0-10 scale 1
• Any trauma history (sharp foods, dental appliances, biting) 3

Critical Pre-Biopsy Laboratory Tests

Order these blood tests before the biopsy appointment: 2

• Complete blood count (to exclude leukemia, anemia, or other blood disorders)
• Fasting blood glucose and hemoglobin A1c (diabetes increases risk of fungal infections)
• HIV antibody and syphilis serology
• Coagulation studies if bleeding risk exists

Red Flags Requiring Immediate Referral

Seek urgent evaluation (within 48 hours) if any of these are present: 1

• Constitutional symptoms: fever, night sweats, weight loss, or general weakness (may indicate lymphoma or systemic infection)
• Multiple ulcers or ulcers in other body locations
• Ulcer larger than 1 cm with irregular borders
• History of tuberculosis (even if treated years ago—oral TB can reactivate)
• Immunosuppression from any cause (diabetes, HIV, chemotherapy, chronic steroids)
• Gastrointestinal symptoms like abdominal pain or diarrhea (Crohn's disease can present with oral ulcers)

What the Biopsy Will Reveal

The pathology will distinguish between: 1

• Malignancy: squamous cell carcinoma (most common), lymphoma (NK/T-cell or other types)
• Infections: tuberculosis (requires special staining for acid-fast bacilli), fungal infections (especially in diabetics)
• Inflammatory conditions: Crohn's disease, Behçet's syndrome, pemphigus, lichen planus
• Simple trauma or aphthous ulceration (diagnosis of exclusion)

If Initial Biopsy Shows Only "Chronic Inflammation"

This non-specific finding requires further action: 1

• Send the specimen to a specialized oral pathologist for expert consultation
• Consider repeat biopsy if the ulcer persists after 2 more weeks
• Screen for systemic diseases with additional testing (chest X-ray for tuberculosis, colonoscopy if GI symptoms present, autoimmune antibodies)

Symptomatic Management While Awaiting Biopsy

Use these measures to control pain, but do not delay the biopsy: 1

• Sodium bicarbonate mouthwash (non-alcoholic): rinse 4-6 times daily, increase to hourly if needed
• Topical anesthetic: viscous lidocaine 2% applied before meals
• Systemic pain control: acetaminophen or NSAIDs for mild-moderate pain; consider short-acting opioids for severe pain interfering with eating
• Avoid irritants: no hot, spicy, sharp, or acidic foods

If Aphthous Ulcer is Suspected (After Malignancy Excluded)

Only after biopsy rules out cancer, consider: 1

• High-potency topical corticosteroid: clobetasol gel 0.05% applied directly to ulcer 2-3 times daily
• Dexamethasone mouth rinse 0.1 mg/ml if multiple locations
• Systemic corticosteroids for severe cases: prednisone 30-60 mg daily for 1 week, then taper over second week (only after infection excluded)

Critical Pitfalls to Avoid

• Never assume a small ulcer is benign—squamous cell carcinoma can present as small lesions, and the 1-month duration is already excessive delay 2
• Do not treat empirically with steroids before biopsy—this can mask malignancy and delay diagnosis 1
• Do not miss synchronous lesions—examine the entire oral cavity, oropharynx, and floor of mouth 2
• Do not overlook risk factors: tobacco use, alcohol consumption, HPV exposure, immunosuppression 2

Bottom line: At 1 month duration, this ulcer has already persisted far beyond the 2-week threshold for mandatory biopsy. Schedule this immediately—the differential includes life-threatening conditions that require urgent diagnosis and treatment. 1, 2