chronic otitis externa

Introduction:

Chronic otitis externa is a chronic inflammation involving the skin lining of the external auditory canal of unknown etiology. Diverse mechanisms from allergy to autoimmune reaction has been implicated. Things which are pretty clear about this condition are that:

1. It is not acute & painful as acute otitis externa
2. It is not an invasive condition involving the skull base (like malignant otitis externa)

Characterstic features:

1. It waxes and wanes showing intervening periods of remissions and exacerbations affecting the quality of life
2. It is bilateral in more than half of these patients
3. Pruritis is common
4. Clear / seromucinous discahrge is seen during periods of exacerbations
5. Aural fullness is also common

Two types of chronic otitis externa have been encountered.

Chronic otitis externa with seborrhoea:

This condition is characterised by lack of cerumen. These patients may have clear ear discharge, sometimes this discharge could be seen admixed with white flakes. The skin lining the external canal may be erythematous and shiny in appearance.

Chronic exematous otitis externa:

This condition is characterised by weepy, moist, erythematous and tender skin in the external auditory canal. It can also spread to involve the pinna causing perichondritis.

Causes of chronic otitis externa:

1. Allergy
2. Contact dermatitis
3. Wegner's granulomatosis
4. Reduced cerumen production
5. Cerumen produced ineffective against pathogens ?

Studies also reveal that the relative humidity is higher and pH is also higher in these ears. If pH could be lowered it would make the environment inhospitable for pathogens.

Role of Dermatophytid reaction in chronic otitis externa:

Low grade fungal infections elsewhere in the body can set up inflammatory allergic reaction in the skin lining the external auditory canal. Hence it is worthwhile making a meticulous search for the presence of fungal infections elsewhere in the body and treating it aggressively. Yeast elimination from diet is strongly advocated. If serum IgE is elevated then immunotherapy could be considered.

Management:

1. Removal of all / potential irritants
2. Topical steroid therapy
3. A course of oral steroid can be administered in refractory cases
4. Topical application of 1% Tacrolimus ( a nonsteroidal immunosuppresant) has been used with reasonable success