creation date: 2026-05-04 18:49
tags: Pathologies
Acute Otitis Externa
Background
Definitions
Acute otitis externa (AOE), also referred to as external otitis or swimmer’s ear is the inflammation of the external auditory canal.
AOE can occur in any age group. It is more likely to occur in the summer, possibly due to ambient humidity and participation in water activities.
Etiology and Risk Factors
The most common pathogen are:
- Pseudomonas aeruginosa (40%)
- Staphylococcus aureus (15%)
- Anaerobic organisms (17%)
- Fungal infection (2-10%), more common with hearing aids and/or post antibiotics use
Risk factors include:
- Swimming or other water exposure
- Trauma from excessive cleaning or aggressive scratching
- Devices the occlude the ear canal (eg. earphones, diving caps, hearing aids)
- Conditions such as allergic contact dermatitis (earring or chemicals), dermatologic conditions (eg. psoriasis, atopic dermatitis)
- Prior radiation therapy (ischemic ear canal changes)
Pathogenesis
The external auditory canal is a cylinder measuring approximately 2.5 cm in length and 7-9 mm in width. In the inner two-third of the canal contains the bony portion, of which there is no subcutaneous tissue and the dermis is in direct contact with the underlying periosteum. This means minimal inflammation or instrumentation can cause significant pain and/or injury.
The inherent defense of the ear canal consist of:
- Tragus and conchal cartilage partially covering the opening to prevent foreign body entrance
- Hair follicles and narrowing of the isthmus to impair entry of contaminants
- Cerumen which creates acidic environment and hydrophobia to prevent ideal culture medium
Pathogenesis of otitis externa follows this sequence:
- Breakdown of the skin-cerumen barrier
- Inflammation and edema leads to pruritus and obstruction
- Scratching creates further injury
- Ear canal becomes dark, warm, alkaline, moist which is ideal for organism growth
Clinical Presentation
Signs & Symptoms
Symptoms are:
- Ear pain
- Pruritus
- Discharge
- Hearing loss
Physical findings include:
- Erythematous and edematous ear canal
- Debris or cerumen (typically yellow, brown, white, or grey)
In severe disease, periauricular erythema, lymphadenopathy, and fever may be appreciated.
Note that otomycosis (fungal) may have different presentation depending on the fungus.
History & Physical Exam
History should include:
- Past history of TM perforation, ear infections, ear surgery or radiation
- History of chronic skin conditions
- Recent ear instrumentation
- Use of devices in the ear canal
Physical exam consist of otoscopy. It is important to look for signs of perforated TM as it may indicate underlying otitis media.
Diagnosis
Criteria
Diagnosis is made clinically.
Work-up
Swab and culture
Cultures are reserved for severe cases as empiric treatment is usually more cost effective. Consider if:
- Severe symptoms (intense pain, complete occlusion due to edema, systemic signs)
- Immunosuppressed
- Chronic otitis externa
- Recurrent AOE
- Recent ear surgery
- Refractory disease
Differential
Other conditions that may mimic bacterial AOE are:
- Otomycosis - mold-like or fine coal dust appearance, pseudomembrane; deep-seated itching, less painful than bacterial otitis externa
- Contact dermatitis - lack of response to treatment; use of ototopical agent that may cause reaction
- Chronic suppurative otitis media
- Carcinoma of ear canal
Red Flags / Complications
Complications include:
- Periauricular cellulitis (erythema, edema, and warmth around the auricle)
- Malignant otitis externa (infection spreads from skin to bone and marrow spaces of skyull base causing necrosis)
Management
Treatment of Infection
Initial steps involve cleaning of the ear canal. This will allow for improved healing and better penetration of topical ear drops.
- Clean using otoscope and loop-tipped ear curette or cotton swab
- Irrigation with 1:1 dilution of 3% hydrogen peroxide and water at body temperature (once TM is confirmed intact)
Patients should be instructed to keep their ears from getting wet during treatment.
- Place cotton ball coated with petroleum jelly during bathing/showering.
- Refrain from swimming/water sports for 7-10 days; competitive swimmings may consider returning after 2-3 days if pain has resolved and they wear well-fitting ear plugs
- Avoid hearing aids or ear buds until resolution; disinfect before use
In cases of mild disease (minor discomfort and pruritus, and minimal canal edema):
- Acetic acid-hydrocortisone x7d + 1 refill to use if symptoms have not resolved
- Antibiotic not necessary
In cases of moderate disease (intermediate degree of pain and pruritus, and partial occlusion of canal), antibiotics are added that can cover S. aureus and Pseudomonas aeruginosa:
- Ciprofloxacin-hydrocortisone
- Ciprofloxacin-dexamethasone
- Neomycin-polymyxin B-hydrocortisone
In cases of severe disease (intense pain, complete edema occlusion):
- Same antibiotics-corticosteroid options as moderate
- Oral antibiotics (oral fluoroquinolone such as levofloxacin 500 mg PO daily x7d) if also febrile
- Wick placement for delivery of medication
In patients with perforated TM or unknown TM status, preferred antibiotics are:
- Ciprofloxacin-hydrocortisone
- Ciprofloxacin-dexamethasone
Additionally, avoid acidic, alcohol, or aminoglycosides; refer to ENT if no improvement in 7 days.
Pain Management
Pain management is often not necessary as relief is rapid after initiation of topical therapy. However, patients who require it will generally respond to oral NSAIDs.