Background Information

Causative Agent

Most common organisms:

• Staphylococcus aureus
• Pseudomonas aeruginosa

Risk Factors

Environmental exposures:

• Water in the ear (esp. polluted water)
• Foreign body in the ear (e.g. earplugs, hearing aids)
• Trauma to the ear canal

Concurrent medical conditions:

• Eczema
• Psoriasis
• Seborrhoeic dermatitis
• Contact dermatitis
• Acute otitis media (purulent middle ear secretions may enter the ear canal if the tympanic membrane is perforated)

Guidelines

Investigation and Diagnosis

Clinical diagnosis in most cases. Only consider ear swabs for microbiology if there is:

• Treatment failure
• Severe / recurrent / chronic otitis externa
• Ear canal occlusion (due to swelling and debris) causing difficulty in applying topical treatments
• Suspected spread of infection beyond the external auditory canal

Suspect acute otitis externa if:

• At least one typical symptom (usually rapid-onset within 48 hours):
  • Itching of the ear canal
  • Ear pain and tenderness of the tragus and/or pinna +/- jaw pain
  • Ear discharge
  • Hearing loss (less common)

• At least two typical signs:
  • Tenderness of the tragus and/or pinna
  • Red and oedematous ear canal
  • Tympanic membrane erythema 
  • Cellulitis of the pinna and adjacent skin
  • Conductive hearing loss (less common)
  • Tender regional lymphadenitis (less common)

Management

Self-Care Measures

• Consider OTC acetic acid 2% ear drops / spray (if ≥12 y/o) for a maximum of 7 days
  • Acetic acid (like vinegar) reduces pH, thus inhibiting bacterial and fungal cell growth

• Keep the ears clean and dry
  • Avoid swimming and water sports for at least 7-10 days
  • Use earplugs and/or tight-fitting cap when swimming
  • Keep shampoo, soap and water out of the ear when bathing and showering (e.g. use earplugs or cotton wool)

• Avoid damage to the external ear canal
  • Do not use cotton buds or other objects to clear the ear canal

Pharmacological Management

Offer paracetamol or ibuprofen as needed for analgesia

Bacterial Infection Likely

1st line: consider 7-14 days of

• Topical antibiotic (gentamicin / ciprofloxacin)
• +/- Topical steroid (prednisolone or betamethasone)

Consider oral antibiotics if the patient is immunocompromised / severe infection / spread beyond the external ear canal (e.g. cervical lymphadenopathy, periauricular cellulitis, skull base osteomyelitis)

• If Pseudomonas is suspected → ciprofloxacin (or aminoglycoside)
• Otherwise → flucloxacillin (if penicillin allergy, use a macrolide – clarithromycin / azithromycin / erythromycin)

Fungal Infection Likely

Consider

• Topical fungal (clotrimazole)
• +/- Topical steroid (prednisolone or betamethasone)

References