Otitis externa
Otitis externa is diffuse inflammation of the external auditory canal, usually bacterial (Pseudomonas or Staphylococcus aureus) and diagnosed clinically by tragal tenderness and canal erythema with otorrhea. Uncomplicated disease is treated with topical antibiotic-steroid otic drops for 7 days, while malignant (necrotizing) otitis externa in a diabetic or immunocompromised patient is skull-base osteomyelitis requiring systemic antipseudomonal therapy and urgent otolaryngology referral.
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What this article covers
- Overview
Otitis externa (AOE) is diffuse inflammation of the external auditory canal, sometimes extending to the pinna and tragus, with rapid onset within the preceding 3 weeks.
- Epidemiology
A common, largely preventable condition associated with swimming, since water exposure washes out the canal's normally acidic, protective environment ("swimmer's ear").
- Risk factors
Frequent water exposure (swimming, showering) that washes out the canal's protective acidic cerumen environment, favoring growth of Pseudomonas, which thrives in a moist environment.
- Pathophysiology
Normal cerumen keeps the external canal acidic and hydrophobic, suppressing bacterial growth; anything that washes out or disrupts this layer (water exposure, trauma, cerumen removal) allows bacterial overgrowth.
- Clinical features
Otalgia, pruritus, and a sensation of ear fullness or otorrhea are the presenting symptoms of uncomplicated otitis externa, evolving rapidly (within 3 weeks) rather than as a chronic process.
- Differential diagnosis
Acute otitis media: bulging or intensely erythematous tympanic membrane with diminished hearing, without tragal tenderness, and canal skin typically unaffected.
- Diagnosis
The diagnosis is clinical: rapid-onset otalgia/otorrhea with tragal or pinna tenderness on examination and canal erythema and edema on otoscopy confirms otitis externa; no specific test is required…
- Management
First, for uncomplicated acute otitis externa, start topical therapy: ciprofloxacin 0.3%-dexamethasone 0.1% otic suspension, 4 drops in the affected ear twice daily for 7 days, or ofloxacin otic…
- Complications
Progression to malignant (necrotizing) otitis externa and skull-base osteomyelitis in a diabetic or immunocompromised host is the most serious complication.
- Prognosis
Uncomplicated otitis externa resolves rapidly with topical therapy, typically within the 7-day treatment course, with an excellent prognosis in an immunocompetent host.
- Prevention
Counsel patients to avoid inserting cotton swabs or other objects into the ear canal, since this both predisposes to infection and can worsen cerumen impaction, causing laceration or tympanic membrane perforation.
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