Otomycosis
Fungal infection of the external auditory canal, usually a superficial colonisation of macerated keratin rather than tissue invasion, accounting for roughly 10 percent of all otitis externa and considerably more in humid tropical settings.
- Aspergillus species cause 60 to 90 percent of cases, with Aspergillus niger predominant, followed by A. fumigatus and A. flavus.
- Candida albicans and C. parapsilosis account for most of the remainder and produce a less visually obvious picture.
- Mixed bacterial and fungal growth is common in previously treated canals.
The canal offers warm humid keratin, an ideal substrate. Disease follows loss of the acidic cerumen film and epithelial disruption. Prolonged antibacterial ear drops are the single most important iatrogenic cause, eliminating competing flora and providing a moist vehicle. Corticosteroid containing drops compound this by local immunosuppression.
Predisposing factors
- Antibacterial or steroid ear drops used beyond 10 to 14 days.
- Humid climate, swimming, occlusive hearing aids and earphones.
- Self instrumentation with cotton buds.
- Open mastoid cavity, which retains keratin and cannot self clean.
- Diabetes mellitus, HIV, chemotherapy, long term corticosteroids.
- Tympanic membrane perforation, which allows fungal colonisation of the middle ear mucosa.
Invasive disease is rare and confined to the immunocompromised, where Aspergillus penetrates the canal floor and produces fungal skull base osteomyelitis with a mortality far exceeding that of pseudomonal disease.

