Otomycosis

Otomycosis is fungal infection of the external auditory canal.

The incidence of otitis external is not known but it is more common in hot climates and is more common in those who indulge in aquatic sports. About 1 in 8 of otitis external infections are fungal in origin. The usual organisms are aspergillus and candida of which about 90% are aspergillus species. The fraction of otitis externa that is otomycosis may be higher in hot climates and much of the literature originates from tropical and subtropical countries. In the UK the diagnosis of otitis externa is made most often in late summer.¹

Factors that predispose to otitis externa include absence of cerumen, high humidity, increased temperature, and local trauma, usually from use of cotton swabs or hearing aids. Cerumen has a pH of 4 to 5 and so suppresses both bacterial and fungal growth. Aquatic sports including swimming and surfing are particularly associated because repeated exposure to water results in removal of cerumen and drying of the external auditory canal. Other predisposing conditions include eczema, allergic rhinitis, and asthma.

The typical presentation is with inflammation, pruritus, scaling, and severe discomfort. The mycosis results in inflammation, superficial epithelial exfoliation, masses of debris containing hyphae, suppuration, and pain.² Pruritis is more marked than with other forms of ear infections.

The initial presentation is similar to bacterial otitis externa but otomycosis is characterized by many long, white, filamentous hyphae growing from the skin surface. Suspicion of fungal infection may arise only when the condition fails to respond to antibiotics. Even if bacteria have been grown, there may be more than one aetiological agent. It is also possible that topical antibiotics have predisposed to the fungal infection.³
An essential piece of history that may easily be missed is a holiday in an exotic place with surfing or SCUBA diving.

Swabs from infected ears should be examined for both bacteriology and mycology. Epithelial debris placed in 10% KOH should reveal the presence of hyphae and in some instances the fruiting structures of the aetiological agent.

Otomycosis is a chronic recurring mycosis. The ear should be cleaned as for otitis externa.⁴

Burrow's solution or 5% aluminum acetate solution should be used to reduce the swelling and remove the debris. An aqueous solution of 1% thymol in metacresyl acetate, or iodochlorohyroxyquin should be considered if drying the ear does not work satisfactorily.

Antifungal ear drops are of value.⁵ Clotrimazole and econazole drops are very effective but may be needed for 1 to 3 weeks. Clioquinol is both antibacterial and antifungal and may be used as eardrops with hydrocortisone in the formulation of Locorten Vioform™ .

Both cleaning of the ear and use of drops represent a problem in the presence of a perforated ear drum. Aminoglycoside drops, for bacterial infection, should be avoided with a perforated drum because of risk of ototoxicity.

Once antifungal therapy is started there is usually good resolution in the immunologically competent.
Aquatic activities may be resumed after a week but precautions should be taken to reduce entry of water to the ears to reduce the risk of recurrence.