Fungal Ear Infection (Otomycosis)

Otomycosis is fungal infection of the external auditory canal.

The incidence of otomycosis is not known but it is more common in hot climates and in those who indulge in aquatic sports. About 1 in 8 of otitis external infections are fungal in origin. 90% of fungal infections involve Aspergillus spp. and the rest Candida spp.¹ The prevalence rate has been quoted as 9% of patients presenting with signs and symptoms of otitis externa.² 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.³

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. There may be a history of previous invasive procedures on the ear.² Other predisposing conditions include eczema, allergic rhinitis, and asthma.¹

The typical presentation is with inflammation, pruritus, scaling, and severe discomfort. The mycosis results in superficial epithelial exfoliation, masses of debris containing hyphae, and suppuration,⁴ Pruritus is more marked than with other forms of ear infections and discharge is often a marked feature.

The initial presentation is similar to bacterial otitis externa but otomycosis is characterised 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.⁵

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% potassium hydroxide 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 canal should be cleared of debris and discharge as this lowers the pH and reduces the activity of aminoglycoside ear drops (see our Otitis Externa article).⁶ Suction can be used if available. Cleaning may be required several times a week. Analgesia is required. If there is an irritant or allergen it must be removed. Keep the ear dry and avoid scratching it with cotton wool buds. Avoid cotton wool plugs in the ear unless discharge is so profuse that it is required for cosmetic reasons. If used keep them loose and change often. .

Burrow's solution or 5% aluminum acetate solution should be used to reduce the swelling and remove the debris.² An aqueous solution of 1% thymol in metacresyl acetate, or iodochlorohyroxyquin should be considered if drying the ear does not work satisfactorily.⁷

Antifungal ear drops are of value.⁸ There is no consensus on treatment but evidence supports the use of topical ketoconazole.² Clotrimazole and econazole drops are very effective but may be needed for 1 to 3 weeks.¹ Clioquinol is both antibacterial and antifungal and may be used as eardrops with hydrocortisone in the formulation of Locorten Vioform™.⁹

A topical aminoglycoside should only be prescribed if there is obvious infection. Topical aminoglycosides should be used for no longer than 7 days (specialists sometimes recommend 14 days) in view of the potential for ototoxicity.⁶

Cleaning of the ear can represent a problem in the presence of a perforated ear drum and a specialist may need to be involved.

Once antifungal therapy is started there is usually good resolution in the immunologically competent. However, the risk of recurrence is high if the factors which caused the original infection are not corrected, and the normal physiological environment of the external auditory canal remains disturbed. These include avoiding sudden manoeuvres in the external auditory canal (e.g. frequent cleaning with a cotton bud), taking care to avoid excessive moisture by not going in the water, and receiving appropriate medical or surgical treatment for otitis externa.¹⁰