D2.102 - Hidden metal triggers in allergic contact dermatitis

Allergic contact dermatitis (ACD) due to metals is a common inflammatory skin disease induced by re-exposure of the skin to contact allergens, being a delayed-type hypersensitivity reaction. Metal-induced ACD has been increasing, affecting 10–15% of the population worldwide. Nickel is the most frequent allergen and often cross-reacts with other metals, mainly cobalt and chromium. Everyday items such as jewelry, buttons, zippers, mobile phones, and leather are common sources of exposure. Patch testing remains the only practical, scientific and objective method to confirm the diagnosis of ACD.

Three cases of ACD due to metals exposure are presented. The diagnosis was established based on detailed history, clinical examination, and patch testing, which is the gold standard for identifying the allergens involved. Patch testing was performed using standardized panels from the European Baseline Series, applied to intact skin and interpreted 72 hours post-application, with reactions induced by nontoxic doses of allergens. Patient A, 35 years old, presented erythematous and vesicular lesions on the earlobes and neck, triggered by jewelry; patch testing showed very strong sensitization to nickel (+++), strong to chromium and colophonium (++), and a mild reaction to paraben mix (+). Patient B, 19 years old, had eczematous lesions on the wrists related to metal accessories; testing confirmed strong sensitization to nickel and cobalt (++). Patient C, 46 years old, experienced recurrent dermatitis on the dorsal hands; testing revealed very strong reactions to nickel and sodium metabisulfite (+++), strong to lanolin alcohol (++), and weak reactions to formaldehyde and methyldibromo-glutaronitrile (+).

The presented cases show nickel emerging as the most frequent sensitizer in all three patients, in agreement with epidemiological data. Metal-induced ACD can present with heterogeneous clinical manifestations, ranging from erythema, edema, pruritus, and vesiculation to chronic lichenified lesions. The condition occurs more frequently in women and can affect individuals of various age groups.

All patients showed improvement following allergen avoidance and targeted patient education, highlighting the importance of patch testing in identifying metal sensitizations.