Allergic contact dermatitis prevalence in patients with otitis externa.

A statistical analysis of the relationship between otitis externa and various clinical and etiological variables was carried out in 64 patients. Between 1988 and 1989, true eczema of the auditory canal was found in 43 of the 64 patients seen sequentially. 23.5% of all the patients found to have dermatitis could be regarded as having allergic contact dermatitis and the allergen identified. This incidence is less than the 40% and the 58% found in other previous studies. We did not find any specific difference in sex and age between the allergic and non-allergic groups. In the allergic group, topical drugs were the commonest sensitizing agents, followed by chemicals and resins found in the ear prosthesis. Twenty-one patients with negative patch tests were classified as seborrheic dermatitis and 11 as atopic dermatitis. The other 19 patients, who were discharged before patch testing, were diagnosed as having psoriasis (8) or chronic bacterial (6) or fungal infections (5), without true blister reaction. We think that accurately selected series must be used for these studies because of the low incidence of allergic contact dermatitis.