Otitis Externa



Inflammation of the external auditory canal:

  • Acute diffuse otitis externa (AOE) (<6 weeks): most common form; infectious etiology most commonly bacterial (Pseudomonas aeruginosa and Staphylococcus aureus); less commonly fungal (Aspergillus and Candida)
  • Chronic otitis externa (>3 months): commonly due to inadequately treated acute otitis externa, persistent allergies, or chronic skin conditions
  • Eczematous otitis externa: may accompany typical atopic eczema or other primary skin conditions
  • Malignant (necrotizing) otitis externa: an infection that extends into the deeper tissues adjacent to the canal; may include osteomyelitis of the mastoid or temporal bone; a medical emergency requiring urgent referral; can be life-threatening; rare, especially in children (1)
  • Synonym(s): swimmer’s ear



  • Annual incidence of ~1% (2)
  • Higher in the summer months and in warm, wet climates
  • Can affect all age groups but has a peak incidence in 7- to 12-year-olds (3)

Lifetime prevalence of 10% (2)

Etiology and Pathophysiology

  • Factors associated with pathogenesis:
    • Skin, cerumen, and surrounding structures provide protection for the integrity of external auditory canal.
    • Cerumen, being a hydrophobic and sticky substance, provides a physical barrier against many foreign particles. Normal cerumen production also creates an environment that is slightly acidic and not favorable for most pathogens.
    • Disruption of the protective skin-cerumen barrier, followed by the subsequent inflammation, swelling, and obstruction of the canal, and impaired cerumen production are all factors in the development of acute otitis externa.
  • AOE, infectious etiology (3):
    • Bacterial infection (>90%): P. aeruginosa (22–62%), S. aureus (11–34%); polymicrobial infection is common.
    • Fungal infection (<10%, more commonly associated with chronic otitis externa): Aspergillus (60–90%), Candida spp. (10–40%)
  • Chronic otitis externa: often occurs due to inadequately treated acute otitis externa, persistent allergies, or chronic skin conditions (2).
  • Eczematous otitis externa (associated with primary skin disorder)
    • Eczema, seborrhea, psoriasis
    • Contact dermatitis
    • Purulent otitis media
    • Sensitivity to topical medications
  • Malignant (necrotizing) otitis externa (1)
    • Invasive bacterial infection: Pseudomonas, increasing incidence of methicillin-resistant S. aureus (MRSA)
    • Associated with patients with diabetes mellitus (DM) or immunosuppression

Risk Factors

  • Acute and chronic otitis externa
    • Water exposure—typically swimming in fresh water
    • Trauma to the external canal—cleaning, scratching, use of instruments
    • Hot, humid weather
    • Use of external devices—hearing aids, ear plugs
    • Dermatologic conditions—eczema, seborrhea, psoriasis
    • Anatomic abnormalities—narrow canal, exostoses
    • Cerumen buildup
    • Previous ear surgery
    • Previous local radiotherapy
  • Eczematous: primary skin disorder
  • Necrotizing otitis externa in adults
    • Advanced age
    • DM
    • Immunosuppression (e.g., AIDS, malignancy)

General Prevention

  • Avoid prolonged exposure to moisture.
  • Use preventive antiseptics (acidifying solutions with 2% acetic acid [white vinegar] diluted 50/50 with water or isopropyl alcohol or 2% acetic acid with aluminum acetate [less irritating]) after swimming and bathing.
  • Treat predisposing skin conditions.
  • Eliminate self-inflicted trauma to canal with cotton swabs and other foreign objects.
  • Treat underlying systemic conditions.
  • Ear plugs when swimming

There's more to see -- the rest of this topic is available only to subscribers.