How should I manage a canker sore (aphthous ulcer)?

Management of Canker Sores (Aphthous Ulcers)

Start with topical high-potency corticosteroids as first-line therapy, combined with pain control measures and good oral hygiene, escalating to systemic therapy only if ulcers persist beyond 2 weeks or fail to respond to initial treatment. 1, 2

First-Line Topical Treatment

Apply topical corticosteroids directly to the ulcer as your primary intervention:

• For localized ulcers: Use clobetasol gel or ointment 0.05% applied to the dried ulcer 2-4 times daily 1
• For multiple or widespread ulcers: Use betamethasone sodium phosphate 0.5 mg dissolved in 10 mL water as a rinse-and-spit solution 2-4 times daily 1, 2
• Alternative for localized lesions: Triamcinolone acetonide 0.1% paste applied directly to dried ulcer 2-4 times daily 1

The British Journal of Dermatology emphasizes that topical corticosteroids should be selected based on ulcer location and extent, with higher potency formulations reserved for more severe cases 1.

Pain Management

Control pain with topical anesthetics before meals to maintain nutrition:

• Apply viscous lidocaine 2% before eating 1, 2
• Use benzydamine hydrochloride rinse or spray every 3 hours, particularly before meals 1, 2
• Consider topical NSAIDs such as amlexanox 5% oral paste for moderate pain 1, 2

Supportive Care and Oral Hygiene

Implement daily oral hygiene measures to prevent secondary infection and promote healing:

• Rinse mouth with warm saline mouthwashes or non-alcoholic sodium bicarbonate mouthwash 4-6 times daily 1, 2
• Use antiseptic oral rinses twice daily (0.2% chlorhexidine digluconate or 1.5% hydrogen peroxide) 1
• Apply mucoprotectant mouthwashes (e.g., Gelclair) three times daily to protect ulcerated surfaces 1
• Apply white soft paraffin ointment to lips every 2 hours if affected 1
• Brush teeth with a soft toothbrush after meals and before sleep using mild fluoride-containing, non-foaming toothpaste 3

Dietary Modifications

Avoid irritating foods and substances that worsen ulceration:

• Eliminate hard, acidic, salty, spicy, hot, raw, or crusty foods 3, 4
• Avoid tomatoes, citrus fruits, and hot drinks 3
• Stop using toothpastes containing sodium lauryl sulfate 4
• Avoid alcohol and carbonated drinks 3, 4

When to Escalate Treatment

If ulcers persist beyond 2 weeks or fail to respond to topical therapy within 1-2 weeks, escalate to second-line treatments:

• Consider intralesional triamcinolone injections weekly (total dose 28 mg) for persistent localized ulcers 1
• Use systemic corticosteroids (prednisone/prednisolone 30-60 mg or 1 mg/kg daily for 1 week, then taper over second week) for highly symptomatic or widespread ulcers 1, 2
• For recurrent aphthous stomatitis (≥4 episodes per year), consider colchicine as first-line systemic therapy 1, 5, 4

The European League Against Rheumatism specifically recommends colchicine for patients with recurrent ulcers, particularly when associated with erythema nodosum or genital ulcers 1.

Critical Diagnostic Pitfall

Rule out oral herpes before starting corticosteroids, as steroids potentiate HSV infection:

• Oral herpes presents with vesicles that rupture into ulcers, often with prodromal tingling and possible systemic symptoms 2
• Aphthous ulcers appear as painful ulcerations without preceding vesicles 2
• Never use topical corticosteroids if herpes is suspected - this distinction is essential because corticosteroids worsen HSV infection while antivirals are ineffective for aphthous ulcers 2

When to Refer

Refer to a specialist for:

• Any ulcer lasting more than 2 weeks despite treatment 1
• Solitary chronic ulcers requiring biopsy to exclude squamous cell carcinoma 5
• Recurrent ulcers requiring systemic immunosuppressive therapy beyond corticosteroids 1

Common Pitfall to Avoid

Do not taper corticosteroids prematurely before disease control is established - the British Journal of Dermatology specifically warns against this practice, which leads to treatment failure 1.