Acute otitis externa (AOE), also known as "swimmer's ear", is inflammation of the external auditory canal (EAC) that can involve the pinna as well. Bacterial infection, most commonly with Pseudomonas aeruginosa, is responsible for the overwhelming majority of cases. It is a common condition.
Acute otitis externa has a 1% annual incidence and a 10% lifetime prevalence 1,2. 98% of acute otitis externa is bacterial in origin 3.
Acute bacterial otitis externa is common in swimmers; swimming in contaminated lakes and rivers increases the risk of pseudomonal otitis externa.
Progression of acute bacterial otitis externa to necrotising (a.k.a. malignant) otitis externa is rare; however, of the patients who develop necrotising otitis externa, more than 90% are reported to have glucose intolerance.
Patients typically present with pain in the pinna and otorrhoea, and there is usually oedema of the external auditory canal (EAC), and sometimes erythema and tenderness of the preauricular soft tissues.
An increase in moisture and lack of defensive, acidic cerumen in the external auditory canal causes oedema and a favourable environment for bacterial overgrowth.
Trauma to the thin epithelial lining of the canal (with cotton applicators or use of hearing aids) can predispose to infection, facilitating Pseudomonas, and to a lesser degree Staphylococcal, overgrowth 4.
Pseudomonas aeruginosa, Staphylococcus epidermidis, and Staphylococcus aureus are the most common isolates in descending order in bacterial otitis externa.
Bacterial otitis externa may range from a brief inconvenience in immunocompetent individuals to life-threatening in immunosuppressed individuals (see necrotising otitis externa).
Otomycosis is primarily caused by Aspergillus and Candida spp. It is a common problem in patients with hearing aids or cerumen impaction, which creates a moist environment, facilitating fungal colonisation, but can also result from primary antibiotic therapy for bacterial otitis externa. Pruritus, discharge, and pain are presenting symptoms.
Rarely, a viral aetiology such as a varicella-zoster virus infection of the external ear canal is possible manifesting as Ramsay Hunt syndrome.
Imaging is rarely required for acute otitis externa but should be considered in immunocompromised and diabetic patients and when assessing for complications (see necrotising otitis externa).
Treatment and prognosis
Topical treatment, sometimes containing antibiotics/antifungals, or corticosteroids to relieve symptoms, or a combination of the above are prescribed.
Aural toileting to remove excess earwax/cerumen can be considered.
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- 2. Raza SA, Denholm SW, Wong JC. An audit of the management of acute otitis externa in an ENT casualty clinic. The Journal of laryngology and otology. 109 (2): 130-3. Pubmed
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