D2.66 - Allergic contact dermatitis to cobalt and concomitant sensitization to nickel and chromium

Allergic contact dermatitis to cobalt is considered uncommon but appears to be increasingly reported. Cobalt sensitization is frequently associated with concomitant allergy to nickel and, less commonly, to chromium. The aim of this study was to evaluate patterns of concomitant sensitization to cobalt, nickel, and chromium, and to describe the clinical and occupational characteristics of affected workers.

We conducted a retrospective descriptive study including patients who underwent patch testing at the Dermato-Allergology Unit of the Occupational Medicine and Occupational Diseases Department of Farhat Hached University Hospital in Sousse over a 30-year period.

A total of 2140 patients were patch-tested during the study period. Cobalt sensitization was identified in 52 cases. The mean age was 43.63 ± 15.32 years, with a male-to-female ratio of 0.93. Most patients were employed in the textile industry (16.3%), followed by the hospitality sector and the construction industry (9.3% each). The mean duration of occupational exposure was 13 ± 9.58 years. The hands were the most frequently affected site (55.8%), followed by the eyelids (13.5%) and the forehead and cheeks (9.6% each). Erythematous-vesicular lesions predominated (55.76%), followed by erythematous-squamous lesions (32.7%). Concomitant sensitization to cobalt and chromium was observed in 38.46% of cases (n = 20), and to cobalt and nickel in 34.61% (n = 18). Triple sensitization to cobalt, chromium, and nickel was found in 9.62% of patients (n = 5). Women were more frequently sensitized to cobalt and nickel than men (66.7% vs. 33.3%), whereas men showed higher rates of concomitant sensitization to cobalt and chromium (60% vs. 40%) and to chromium and nickel (60% vs. 40%). No statistically significant associations were identified.

The widespread presence of cobalt, nickel, and chromium in both occupational and non-occupational environments makes avoidance challenging. These findings highlight the need for targeted individual preventive measures and improved exposure control in at-risk occupations.