What is the treatment for allergic otitis externa?

Treatment for Allergic Otitis Externa

The primary treatment for allergic otitis externa is removal of the sensitizing agent and application of a topical steroid such as hydrocortisone aceponate or tacrolimus 0.1% ointment/pimecrolimus 1% cream without antibiotics. 1

Identification and Management

Diagnosis

• Look for characteristic signs:
  • Erythema, pruritus, skin inflammation, edema of the external auditory canal
  • Persistent otorrhea despite conventional treatment
  • Possible blisters and vesicles in severe cases
  • Reaction may extend beyond ear canal to surrounding skin
  • Maculopapular or eczematous eruption on conchal bowl and ear canal
  • Possible erythematous streak extending down pinna where drops contact skin

Common Allergens

1. Topical medications:

   • Neomycin (most common - 13-30% prevalence on patch testing) 1
   • Other antibiotics: bacitracin, quinolones, polymyxin B sulfate
   • Steroid preparations: hydrocortisone, triamcinolone
   • Topical anesthetics: benzocaine, dibucaine, tetracaine

2. Preservatives and vehicles:

   • Propylene glycol
   • Thimerosal
   • Benzalkonium chloride
   • Benzyldimethylbenzylammonium chloride
   • Methyl-p-oxybenzoate
   • Fragrance additives

3. Physical devices:

   • Silicone ear plugs
   • Hearing aid molds containing silicone or methyl-methacrylate
   • Nickel in earrings (affects ~10% of women with pierced ears) 1

Treatment Algorithm

Step 1: Identify and Remove Allergen

• Discontinue all potentially sensitizing topical medications
• Consider patch testing to identify specific allergens 2
• Avoid further contact with identified allergens

Step 2: Anti-inflammatory Treatment

• Apply topical steroid without antibiotics:
  • Group III steroid solutions (like betamethasone dipropionate 0.05%) have shown superior efficacy compared to combination antibiotic-steroid preparations 3
  • Alternatives: tacrolimus 0.1% ointment or pimecrolimus 1% cream 1

Step 3: Ear Care

• Gentle cleaning of the ear canal if needed
• Avoid water exposure during acute phase
• Avoid insertion of foreign objects into the ear

Step 4: Follow-up

• Reassess after 1-2 weeks
• If symptoms persist, consider:
  • Alternative diagnosis
  • Patch testing if not done previously
  • Specialist referral if refractory to treatment

Evidence-Based Considerations

Research shows that topical steroids alone can be effective for treating allergic otitis externa without antibiotics. A randomized controlled trial demonstrated that betamethasone dipropionate 0.05% solution was significantly more effective than combination hydrocortisone with antibiotics for treating external otitis, with less bacterial and fungal growth at follow-up and reduced itching 3.

Common Pitfalls to Avoid

1. Misdiagnosis: Allergic otitis externa can be misdiagnosed as bacterial or fungal infection, leading to inappropriate antibiotic treatment that may worsen the condition.

2. Continued exposure to allergens: Failure to identify and remove the sensitizing agent will result in persistent symptoms.

3. Overuse of antibiotics: Using combination antibiotic-steroid preparations when not needed can lead to bacterial resistance and may worsen allergic reactions 4.

4. Neglecting patch testing: For recurrent or persistent cases, patch testing is valuable to identify specific allergens 2.

5. Overlooking cross-reactivity: Patients sensitized to one topical agent may react to chemically related compounds.

Remember that once a patient has been sensitized, subsequent exposure to the allergen leads to a more pronounced inflammatory response that begins shortly after reexposure 1. Therefore, proper identification and avoidance of allergens is crucial for long-term management.