How to treat a canker sore on the lip?

Treatment of Canker Sores on the Lip

For canker sores (aphthous ulcers) on the lip, start with topical corticosteroid rinses—specifically betamethasone sodium phosphate 0.5 mg dissolved in 10 mL of water as a 2-3 minute rinse-and-spit solution four times daily—combined with topical anesthetics like benzocaine for pain relief. 1, 2

First-Line Treatment Approach

Topical Corticosteroids (Primary Treatment)

• Apply betamethasone sodium phosphate 0.5 mg in 10 mL water as a rinse-and-spit preparation four times daily for inflammatory control 1, 3
• For localized lesions directly on the lip, use clobetasol 0.05% ointment mixed in 50% Orabase twice weekly applied directly to the dried lesion 1
• Alternatively, fluticasone propionate nasules diluted in 10 mL water twice daily can be effective 1

Pain Management

• Benzocaine topical gel applied up to 4 times daily provides temporary pain relief and is FDA-approved for canker sores 2
• Viscous lidocaine 2% (15 mL per application) up to 3-4 times daily for severe pain 1, 4
• Benzydamine hydrochloride oral rinse every 3 hours, particularly before eating, reduces pain and inflammation 1, 3

Protective Barrier and Supportive Care

• Apply white soft paraffin ointment to the lips every 2 hours to protect and moisturize the affected area 3
• Gelclair mucoprotectant gel three times daily forms a protective barrier over ulcerated surfaces 1, 3
• Clean the mouth daily with warm saline mouthwashes to reduce bacterial colonization 1, 3
• Use 0.2% chlorhexidine digluconate mouthwash twice daily as an antiseptic rinse 1, 4

Dietary and Lifestyle Modifications

• Avoid crunchy, spicy, acidic foods and hot beverages during the healing period 1, 4
• Avoid alcohol-containing mouthwashes which cause additional irritation 3, 4

Second-Line Treatment for Refractory Cases

If the canker sore does not improve within 7-10 days with first-line therapy:

• Tacrolimus 0.1% ointment applied twice daily for 4 weeks for recalcitrant lesions on the lips 5, 1
• Intralesional triamcinolone (total dose 28 mg weekly) in conjunction with topical clobetasol for non-healing ulcers 1

Systemic Therapy for Severe Cases

Reserved for cases where topical therapy has failed and quality of life is significantly impacted:

• High-dose oral prednisone 30-60 mg (or 1 mg/kg) for 1 week, followed by dose tapering over the second week 1

When to Investigate Further

Obtain blood work and consider biopsy if ulcers persist beyond 3 weeks despite appropriate treatment 1:

• Full blood count to rule out hematologic disorders 1
• Fasting blood glucose to identify diabetes as a predisposing factor 1
• HIV antibody and syphilis serology if risk factors present 1

Critical Pitfalls to Avoid

• Do not confuse canker sores (aphthous ulcers) with herpes labialis (cold sores), which require antiviral therapy with aciclovir, famciclovir, or valaciclovir 5
• Herpes labialis typically presents with vesicles that progress to ulceration and crusting, often with a prodrome of itching and burning 5
• Stop benzocaine use if symptoms do not improve in 7 days or if irritation, pain, or redness worsens 2
• Oral ulcers may be the first manifestation of systemic diseases including Crohn's disease, Behçet's disease, or hematologic malignancies 1
• Hyperglycemia is an important predisposing factor for invasive fungal infections presenting as oral ulcers 1

Treatment of Secondary Infections

If candidal infection is suspected (white coating, burning sensation):

• Nystatin oral suspension 100,000 units four times daily for 1 week 1, 3
• Or miconazole oral gel 5-10 mL held in mouth after food four times daily for 1 week 1, 3