Otitis Externa



  • Diffuse inflammation of external auditory canal with or without infection
  • Also known as “swimmer’s ear”
  • May be categorized as acute, chronic, or malignant
    • Acute: rapid onset, usually bacterial
    • Chronic: lasting longer than 4 weeks or occurring 4 or more times in 1 year, usually due to nonbacterial causes such as atopic or allergic contact dermatitis from contact with metal, plastic, or chemicals
    • Malignant or necrotizing: extension of infection to osteomyelitis of the base of the skull; more common in immunocompromised patients (e.g., HIV, diabetes)


  • Peaks in children ages 5 to 14 years
  • Uncommon in children age <2 years
  • Peaks in summer months in temperate climates; occurs year-round in warm/humid climates


Annual incidence is 8.1/1,000 in the general population.


Affects 3–5% of the population

Risk Factors

  • Prolonged exposure to water (e.g., frequent swimming, shampooing, long showers, excessive sweating) leading to impaired natural defense mechanisms in external ear
  • Microfissures from trauma
  • Debris from dermatologic conditions (e.g., atopic or seborrheic dermatitis)
  • Use of external devices (e.g., hearing aids or ear plugs)
  • Obstruction of ear canal (e.g., by impacted cerumen, foreign body, sebaceous cyst)
  • Chronic otorrhea or purulent otorrhea from otitis media
  • Drainage from tympanostomy tubes
  • Hairy ear canal
  • Anatomic abnormalities
    • Stenosis of ear canal
    • Exostoses (abnormal bone growth within the ear canal)
  • History of radiotherapy leading to damaged epithelium, desquamation, and diminished cerumen production

General Prevention

  • Elimination of predisposing factors when feasible is the key to prevention.
  • Avoid exposure to excessive moisture.
    • There are no randomized trials evaluating preventive strategies. It may be helpful to instruct swimmers to keep their ears as dry as possible by toweling off, tilting the head to assist with drainage, and using a hair dryer to the ear canal on the lowest setting.
    • Some experts also recommend the use of ear plugs, although this strategy is controversial because it may lead to cerumen impaction, predisposing to otitis externa (OE).
    • Use of a 1:1 alcohol-to-vinegar solution before and after swimming and again before bedtime also may decrease the rate of recurrence.
  • Avoid trauma to the ear canal—in particular, avoid cotton-tip swabs or other cleaning devices.
  • Manage underlying dermatologic conditions.


  • The ear canal is lined with apocrine and sebaceous glands that produce cerumen.
  • Cerumen serves as a barrier to excessive moisture and may help prevent infection due to lysozyme activity and a slightly acidic pH that helps inhibit the growth of pathogenic bacteria.
  • With prolonged exposure to water, cerumen may be washed away and no longer be able to serve this barrier function.
  • Too much cerumen can also lead to entrapment of debris and water retention, thus predisposing to infection.
  • In certain dermatologic conditions, the integrity of the keratin layer may be affected by excessive desquamation.
  • Local trauma to the external canal may also predispose to infection.


  • In the United States, bacterial agents are implicated in >90% of cases and most commonly include Pseudomonas aeruginosa and Staphylococcus aureus.
  • May be polymicrobial in up to 30% of cases
  • Fungal causes include Aspergillus niger and Candida and are more likely in cases of chronic OE or after antibiotic treatment of OE.
  • Viral infections (in particular, varicella-zoster leading to Ramsay Hunt syndrome) account for a minority of cases.

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