INTRODUCTION

Ear eczema is a pruritic inflammatory dermatosis whose prevalence ranges from 7% to 19% [1,2]. It accounts for 23% in Europe and 4% in the U.S. [3,4]. The causes are multiple, dominated by allergic contact dermatitis to metals, topical ear medications, cosmetics, and external hearing aids [5]. Patch tests based on the European Standard Battery are the reference tools for investigating contact allergens. However, in Africa, they remain limited by their availability and the high cost in certain countries with low income. This explains the paucity of data in the literature on contact allergens. The aim of this study was to determine the epidemiological characteristics of ear eczema and to identify the main contact allergens.

PATIENTS AND METHODS

This was a descriptive, cross-sectional study with prospective recruitment over a seven-month period from January 15 to August 15, 2023, at the Dermatology Departments of Aristide le Dantec Hospital, the Institute of Social Hygiene and the Institute of Medical and Social Welfare of Cheikh Anta Diop University, and the Cervico-Facial Department of Fann Hospital. All patients with ear contact dermatitis were included in the study. The diagnosis of eczema was clinical. All patients underwent patch testing using the European Standard Battery. Nickel spot tests on personal products were performed in cases of suspected nickel allergy. A 1% alcoholic solution of dimethylglyoxime combined with a 10% ammonium hydroxide solution (spot test) produced a reddish-pink coloration by precipitation of insoluble salts in the presence of nickel. This test was sensitive from a level of 10 ppm (Fig. 1). Data entry and analysis were performed using SPSS, version 18.

Figure 1: Positive nickel spot test.

RESULTS

We recorded 46 cases of ear eczema, with a hospital frequency of 0.46%. The patients were male in 21 cases (45%) and female in 25 cases (54%), giving a sex ratio of 0.84%. The mean age of patients was 22 years, with extremes of 5 months to 85 years (Fig. 2). Personal atopy was noted in 37 cases (80%) and familial atopy in 28 cases (60%). The atopic equivalents were atopic dermatitis in 22 cases, allergic rhinitis in 21, asthma in 11, and allergic conjunctivitis in 5. Ear hygiene habits included using cotton swabs in 14 cases, washing the ears with fishing nets in 30, using cosmetic creams in 5, and using topical ear medications in 3.

Figure 2: Distribution of the cases by age group.

Other exposure factors included wearing metal earrings in 22 cases, using earphones in 7 cases, and using hearing aids in one case. The management was provided by a dermatologist in 26 cases (56%), a general practitioner in 5 cases (11%), a pediatrician in 4 cases (8%), an ENT specialist in 2 cases (4%), and a traditional practitioner in 6 cases (13%). It was the first episode in 16 cases (34%) and an on-and-off eczema in 30 cases (65%). Table 1 lists the various elementary ear lesions. Ear eczema lesions were chronic in 28 cases (Fig. 3) and acute in 18 cases. The outer ear was the site of lesions in 30 cases (65%), with both ear and symmetrical lesions. Ear lesions were isolated in 17% of the cases, and associated with face eczema in 10%, the hands in 13%, and the scalp in 6%. External auditory canal lesions were noted in 4% of the cases (Fig. 4). Table 2 lists the topography of ear lesions. Epicutaneous tests were conducted in all patients, with polysensitization in all cases. The main contact allergens were nickel in 6 cases (Fig. 5), cobalt in 5, and thiuram mix in 4. Table 3 lists the different contact allergens observed. The relevance of allergological tests was current in 64% of the cases and longstanding in 57%. Concordance between the standard European Battery and the personal products reported by the patient reinforced relevance in 2 cases. The nickel spot test reinforced relevance in 5 cases. Patients had received topical steroids in 40 cases (86%) and moisturizer in 32 cases (69%). Systemic treatments were antihistamines in 36 cases (78%), antibiotics in 5 cases (10%), and oral steroids in 2 cases (4%). The evolution was favorable in 34 cases (73%), with a relapse in 12 cases (26%).

Table 1: Distribution of the cases according to elementary ear lesions.

	Figure 3: Acute allergic contact dermatitis to nickel.
	Figure 4: Allergic contact dermatitis of the external auditory canal.

Table 2: Distribution of patients by ear lesion topography.

Figure 5: Nickel positive patch test.

Table 3: Distribution of the patients according to the different contact allergens identified.

DISCUSSION

We report a hospital incidence rate of 0.46% for ear eczema in Dakar. However, ear eczema remains frequent in allergological consultations, with a prevalence varying between 7% and 19% in American and European series [1,2]. In a European series conducted over an eighteen-year period, with a study population of 10,532 patients, 23% had ear eczema [3]. In the American series, ear eczema accounted for 4.2%, with a study population of 4,3570 patients, conducted over a seventeen-year period [4]. The average age of our patients was 22, with a peak between 2 and 10 years, which corresponded to a link with the high frequency of atopic dermatitis in this age group. According to some authors, ear dermatitis is one of the circumstances in which atopic dermatitis is discovered in children [6]. We noted a predominance of female ear eczema in our study, which corresponded to a link with data reported in the literature [7,8]. This seems to be linked to the wearing of costume jewelry by women. Personal atopy was noted in 80% of our patients, and it is often the sole cause of ear eczema in infants, with a reported frequency of 16% in adults [9]. We noted chronic eczema lesions in 60% of our patients, often linked to delayed diagnosis. The ignorance of our patients could explain the absence of initial specialized care. The external ear auricle was the most frequent site of ear eczema, in 63% of the cases, sometimes associated with damage to the external auditory canal, in 13%. Isolated eczema of the external auditory canal often constitutes a differential diagnosis with psoriasis of the external auditory canal, which is frequent, in 18% of cases, although pruritus is less marked in psoriasis where the scales are thicker [10]. Allergological investigations are the main tools for the etiological search to establish allergenic avoidance measures [11,12]. Patch tests were positive for nickel in all patients, often with poly-sensitization to metals. Metal contact allergens were nickel in 42% of the cases and cobalt in 35%. Nickel is an eyelid allergen reported in 44% of cases in Senegal [13]. In Europe, authors report a 58% frequency of nickel allergy during ear contact dermatitis [14]. Nickel sensitization is frequently triggered by repeated skin contact with objects releasing nickel in excessive quantities, such as costume jewelry. Piercing and earrings also increase nickel sensitization [7,14,15]. Researchers have demonstrated that nickel sensitization is possible when an object in contact with the skin releases more than 0.5 μg of nickel per cm2/week [15]. The nickel test detectable with dimethylglyoxime has a specificity of 98% and a sensitivity of 59% [7,16]. In our study, the nickel test reinforced the relevance of patch tests in 66% of ear CAD cases in women wearing earrings. Nickel is also found in cosmetics and handled objects such as keys, coins, toys, and computers [17,18]. Cobalt is the second most common metal, in 30% of the cases, with a frequency that varies from 8% in Europe to 7.4% in the U.S. [19]. Cobalt is commonly combined with other metals, such as nickel [20]. Cobalt alloys are used in the manufacturing of costume jewelry, clothing accessories, dental materials, implants, and prostheses [20]. Allergic contact face dermatitis was associated with allergic contact dermatitis of the ears in 10% of the cases, with a predominance of women. The more frequent use of cosmetic products in women may be a contributing factor. The implementation of cosmetovigilance measures could lower the incidence of allergic contact dermatitis due to these allergens.

CONCLUSION

Ear eczema is a frequent complaint in dermato-allergology. In Senegal, the causes are still dominated by atopic dermatitis and allergic contact dermatitis to metals and cosmetics. The availability of allergy tests using the Standard European Battery and allergy tests using personal hygiene products allows the monitoring of new contact allergens in Senegal, and effective cosmetovigilance and avoidance measures may be put in place.

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