Otitis externa (OE) refers to inflammation of the external auditory canal, which is most often the result of a local bacterial infection. Risk factors for OE include injury to the skin of the external auditory canal and/or exposure to water. OE is characterized by ear pain, discharge, and tragal tenderness. Otoscopy may reveal a furuncle (localized OE) or a red, edematous external auditory canal (diffuse OE). OE is primarily a clinical diagnosis. Treatment involves keeping the external auditory canal dry and administering fluoroquinolone and hydrocortisone ear drops. Systemic antibiotic therapy is usually indicated in immunosuppressed and/or diabetic patients who are at risk of a more severe variant called malignant otitis externa (MOE). MOE, which is almost always caused by Pseudomonas aeruginosa, may present with facial nerve palsy and is potentially fatal because it spreads rapidly to the base of the skull. Immediate referral and treatment with systemic antipseudomonal antibiotics are indicated.
- Most cases of otitis externa are infectious in origin.
- Bacterial infections (most common cause of otitis externa)
- Fungal infections (less common): Aspergillus (accounts for 90% of all fungal otitis externa), Candida
- Viral infections (rare): Herpes zoster, Influenza viruses
- Risk factors
- Non-infectious forms of otitis externa are less common and include
Subtypes and variants
Malignant otitis externa (necrotizing otitis externa) 
- Definition: necrotizing inflammation of the external auditory canal causing osteomyelitis
- Pathogen: : Pseudomonas aeruginosa (95% of cases)
- Risk factors
- Clinical features
- Prompt IV antibiotic therapy for several weeks
- Surgical debridement is indicated for abscess drainage and removal of bony sequestrum
- Topical antibiotic treatment (see “Therapy” below)
- Prognosis: The mortality rate is high even with appropriate antibiotic therapy
Malignant otitis externa is a severe infection that is often lethal.
- Otitis externa is primarily a clinical diagnosis.
- Check blood glucose levels to rule out diabetes
- Culture and sensitivity tests are not routinely performed; they may be indicated if antibiotic treatment is not effective.
Topical treatment (initial treatment of uncomplicated otitis externa)
- Antibiotic eardrops; (typically ofloxacin, ciprofloxacin, or gentamicin)
- Topical preparations with corticosteroids (e.g., hydrocortisone, prednisolone) to control itching and inflammation
- Aural toilet: clean the external auditory canal and keep it dry using an ear wick and/or astringents (e.g., mixture of isopropyl alcohol and acetic acid)
- Systemic treatment: oral ciprofloxacin (in addition to topical treatment)
- Frequent swimmers should keep the auricle and external auditory canal clean and dry.
- Treat underlying chronic dermatologic conditions.
- Hearing aids should be removed and cleaned regularly.
- Recommend that the patient avoids manipulation of the ear canal (e.g., use of cotton buds to clean the ear).