Otitis Externa
Basics
Description
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: swimmer’s ear
Epidemiology
Incidence
- 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)
Prevalence
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%), Staphylococcus aureus (11–34%); polymicrobial infection is common.
- Fungal infection (<10%, more commonly associated with chronic otitis externa): Aspergillus (60–90%), Candida species (10–40%)
- Chronic otitis externa etiology: often occurs due to inadequately treated acute otitis externa, persistent allergies, or chronic skin conditions (2)
- Eczematous otitis externa (associated with primary skin disorder) etiology:
- Eczema, seborrhea, psoriasis
- Contact dermatitis
- Purulent otitis media
- Sensitivity to topical medications
- Malignant (necrotizing) otitis externa etiology (1):
- Invasive bacterial infection: Pseudomonas, increasing incidence of methicillin-resistant Staphylococcus aureus (MRSA)
- Associated with patients with diabetes or immunosuppression
Risk Factors
- Acute and chronic otitis externa
- Water exposure—typically swimming in fresh water
- Hot, humid weather; sweating
- Trauma to the external canal—cleaning, scratching, use of instruments
- Foreign body
- Use of external devices—hearing aids, ear plugs
- Anatomic abnormalities—narrow canal, exostoses
- Dermatologic conditions—eczema, seborrhea, psoriasis
- Cerumen buildup
- Excessive hair in canal
- Previous ear surgery
- Previous local radiotherapy
- Eczematous: primary skin disorder
- Necrotizing otitis externa in adults
- Advanced age
- Diabetes mellitus
- Immunosuppression (e.g., AIDS, malignancy)
General Prevention
- Avoid prolonged exposure to moisture.
- Use a hair dryer on a low setting to dry the canal.
- Use a head-tilt maneuver to remove excess water.
- 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.
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Citation
Domino, Frank J., et al., editors. "Otitis Externa." 5-Minute Clinical Consult, 33rd ed., Wolters Kluwer, 2025. Medicine Central, im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688572/all/Otitis_Externa.
Otitis Externa. In: Domino FJF, Baldor RAR, Golding JJ, et al, eds. 5-Minute Clinical Consult. Wolters Kluwer; 2025. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688572/all/Otitis_Externa. Accessed October 6, 2024.
Otitis Externa. (2025). In Domino, F. J., Baldor, R. A., Golding, J., & Stephens, M. B. (Eds.), 5-Minute Clinical Consult (33rd ed.). Wolters Kluwer. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688572/all/Otitis_Externa
Otitis Externa [Internet]. In: Domino FJF, Baldor RAR, Golding JJ, Stephens MBM, editors. 5-Minute Clinical Consult. Wolters Kluwer; 2025. [cited 2024 October 06]. Available from: https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688572/all/Otitis_Externa.
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