Metal allergen of the 21st century--a review on exposure, epidemiology and clinical manifestations of palladium allergy.

Consumers are mainly exposed to palladium from jewellery and dental restorations. Palladium contact allergy is nearly always seen together with nickel allergy, as palladium and nickel tend to cross-react. We aimed to analyse the available palladium patch test data and case reports to determine whether the prevalence of palladium mono-sensitization has increased. Based on available patch test data from the period 1986-2008, a total of 10 778 patients were patch tested with palladium chloride. The median prevalence of palladium allergy was 7.8% (range <1.0-19.0%) in dermatitis patients and 7.4% (range 1.3-13.9%) in dental patients. The median prevalence of palladium mono-sensitization (defined as the presence of palladium allergy and the absence of nickel allergy) was 0.2% (range 0-1.6%) in dermatitis patients and 0.5% (range 0-7.2%) in dental patients. A slight increase in the prevalence of palladium mono-sensitization was observed over the study period. We conclude that clinically relevant palladium allergy should mainly be suspected in patients who present with allergic contact granulomas at sites of piercing, but also in patients who have clinical disease and palladium patch test reactivity without concomitant nickel reactivity. Palladium salts should be included in dental screening patch test series. Palladium use in jewellery should be limited until we know more about the risk of sensitization.