What are the causes and recommended treatments for painful oral ulcers?

Painful Mouth Sores: Causes and Treatment

For painful mouth sores, first identify if they are simple recurrent aphthous ulcers (RAU) or require further workup—if ulcers persist beyond 2 weeks or don't respond to 1-2 weeks of treatment, you must obtain blood work and consider biopsy to rule out serious systemic disease, malignancy, or infection. 1

Initial Assessment and Common Causes

The most common painful oral ulcers are:

• Recurrent Aphthous Ulcers (RAU): Well-demarcated, oval/round ulcers with white or yellow pseudomembrane and surrounding red halo 1
• Traumatic ulceration: Location and shape correspond to mechanical irritant (sharp tooth, denture, etc.) 1
• Infectious causes: Viral (HSV, HIV), bacterial (tuberculosis, syphilis), fungal 1, 2
• Medication-related ulceration 2
• Autoimmune/systemic disease: Behçet's disease, inflammatory bowel disease, pemphigus, lichen planus 1, 2

Treatment Algorithm

For Simple RAU (Minor Aphthous Ulcers)

Start with topical therapy first 3:

1. First-line: Topical antiseptics (triclosan) and local anesthetics (lidocaine) for pain relief 3
2. Second-line: Topical corticosteroids if antiseptics/anesthetics fail 3
3. Adjunctive measures:
   • Avoid hard, acidic, salty foods
   • Avoid toothpastes with sodium lauryl sulfate
   • Avoid alcohol and carbonated drinks 3

For Severe or Recurrent Cases

If topical therapy fails, escalate to systemic treatment 3:

• Colchicine: Suitable for most recurrent aphthous stomatitis, especially Behçet's-related 4
• Pentoxifylline or oral prednisolone: For severe cases 3
• Thalidomide: Most effective but reserved for refractory cases due to significant adverse effects 4, 5

Critical Red Flags Requiring Immediate Workup

You must obtain blood work and biopsy if 1:

• Ulcers persist >2 weeks
• No response to 1-2 weeks of treatment
• Multiple sites with different morphologies
• Suspected systemic disease

Required Blood Tests 1:

• Full blood count: Rule out anemia, leukemia, neutropenia
• Coagulation studies: Pre-biopsy safety
• Fasting blood glucose: Hyperglycemia predisposes to fungal infections
• HIV antibody and syphilis serology: Rule out infectious causes
• Iron, folate, vitamin B12: If anemia suspected
• Serum autoantibodies (Dsg1, Dsg3, BP180, BP230): If bullous disease suspected

When to Biopsy

Any solitary chronic ulcer must be biopsied to rule out squamous cell carcinoma 4. Multiple biopsies are needed if ulcers involve multiple sites with different characteristics 1.

Common Pitfalls to Avoid

1. Missing systemic disease: Oral ulcers can be the first manifestation of inflammatory bowel disease, celiac disease, HIV, or hematologic malignancy 1, 4
2. Delaying biopsy: Chronic ulcers (>2 weeks) require tissue diagnosis—don't continue empiric treatment indefinitely 1
3. Overlooking nutritional deficiencies: Check iron, folate, B12 in recurrent cases 4, 5
4. Ignoring medication history: Many drugs cause oral ulceration 2
5. Assuming all ulcers are benign: Tuberculosis presents as stellate ulcers with undermined edges; malignancy must always be excluded in chronic cases 1, 4

Special Considerations

For patients with diabetes: Consider fungal infection as hyperglycemia is a major predisposing factor 1

For suspected bullous diseases: Direct immunofluorescence and serum autoantibodies are essential before and after biopsy 1

Treatment goals 5:

• Primary: Pain relief, reduce ulcer duration, restore oral function
• Secondary: Reduce recurrence frequency and severity