Aetiology of acute diffuse otitis externa

Pseudomonas aeruginosa and Staphylococcus aureus are the most common causes of acute diffuse otitis externa; other bacterial causes are much less common.

Fungal infection (otomycosis) occurs less frequently than bacterial infection, and usually follows the prolonged use of antimicrobial eardrops. Candida or Aspergillus species are the most common fungal pathogens.