Acute otitis externa

Patients typically present with pain in the pinna, otorrhoea and there is usually oedema of the external auditory canal (EAC) and sometimes erythema and tenderness of the preauricular soft tissues

Acute otitis externa has a 1% annual incidence and and 10% lifetime prevalence 1,2. Furthermore, 98% of acute otitis externa is bacterial in origin 3.

Acute bacterial otitis externa is common in swimmers and swimming in contaminated lakes and rivers increases the risk of Pseudomonal otitis externa.

Progression of acute bacterial otitis externa to malignant otitis externa (MOE) is rare, however of the patients who develop MOE, more than 90% are reported to have glucose intolerance.

An increase in moisture and lack of defensive, acidic cerumen in the external auditory canal causes oedema and a favorable 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 bacterial AOE in descending order.

Bacterial AOE may range from a brief problem in immunocompetent individuals to life-threatening in immunosuppressed individuals (necrotising otitis externa).


Otomycosis is primarily caused by Aspergillus and Candida. It is a common problem in patients with hearing aids or cerumen impaction creating a moist environment facilitating fungal colonisation, but also can follow primary antibiotic therapy for bacterial otitis externa. Pruritus, discharge and pain can be present.


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 patients, or when looking for complications (see necrotising otitis externa).

Topical treatments, sometimes containing antibiotics/antifungals, or corticosteroids to relieve symptoms, or a combination of the above are prescribed.

Aural toileting to remove excess wax/cerumen can be conisdered.

Share article

Article Information

rID: 51124
System: Head & Neck
Tag: cases
Synonyms or Alternate Spellings:
  • AOE
  • Acute bacterial otitis externa
  • Acute fungal otitis externa
  • Swimmer's ear
  • Tropical ear

Support Radiopaedia and see fewer ads

Updating… Please wait.

Alert accept

Error Unable to process the form. Check for errors and try again.

Alert accept Thank you for updating your details.