Nickel Persists, Chromium Declines: A 26-Year Perspective on Metal Sensitization and Clinical Relevance from Turkey

BACKGROUND: Metal allergens remain major causes of allergic contact dermatitis (ACD) worldwide. In Turkey, restrictions on nickel release (2018) and hexavalent chromium in leather (2018) and cement (2022) have been implemented, but their impact remains unclear. OBJECTIVES: To assess long-term metal sensitization patterns and evaluate occupational/nonoccupational metal-related ACD. METHODS: We retrospectively analyzed 2932 patients patch-tested with nickel sulfate 5% pet., cobalt chloride 1% pet., potassium dichromate 0.5% pet., and palladium chloride 1-2% pet. (1996-2021). Multivariate logistic regression identified independent predictors of sensitization. RESULTS: The overall prevalence of sensitization to baseline metals was 28.4%. Nickel was the most frequent sensitizer (21.1%), followed by chromium and palladium (both 8.9%), and cobalt (7.1%). Current clinical relevance was highest for chromium (67.4%) and cobalt (51.2%). Occupational ACD (47.5%) was mainly related to chromium/cobalt exposure from cement and metal tools, predominantly affecting the hands, with a notable airborne involvement. Chromium sensitization declined over time. Nickel predominated in nonoccupational ACD and dietary nickel-related systemic allergic dermatitis (SAD) (4.8%), with frequent palladium-nickel cosensitization. Metal device/implant allergy was rare (3.5%). Multivariate analysis identified female sex and younger age as predictors of nickel sensitization, whereas male sex and occupational exposure predicted chromium sensitization. CONCLUSIONS: Metal sensitization remains highly prevalent in Turkey, particularly nickel sensitization. The decline in chromium sensitization likely reflects changes in construction practices. The association between nickel sensitization and SAD highlights the importance of systemic exposure in clinical management.