Reactivity to euro coins and sensitization thresholds in nickel-sensitive subjects

The 1- and the 2-euro coins consist of nickel alloys, which release nickel. The nickel released by far exceeds the amount allowed by the European Union Nickel Directive referring to products intended to come into direct and prolonged contact with the skin. As there is only temporary contact with the skin, the clinical relevance of nickel-containing coins with regard to nickel dermatitis is a matter of debate, although there is evidence that the nickel released from the coins affects some nickel-sensitive subjects through occupational exposure.

Our aim was to study skin reactivity to euro coins, and to correlate the frequency and intensity of coin patch test responses to sensitization thresholds to nickel.

Sixty-four nickel-sensitized and 30 non-nickel-sensitized subjects were patch tested with serial dilutions of nickel sulfate (5, 1, 0.5, 0.1, 0.05, 0.01 and 0.005% in distilled water) and with coins. Italian coins (500, 200, 100 and 50 lira) and euro coins (2 and 1 euros, 20 and 5 euro cents) were used for patch testing and compared.

The application of 1- and 2-euro coins to the skin induced eczematous reactions, being more frequent and intense in comparison with those provoked by other coins. A correlation between intensity of responses to coin patch tests and sensitization threshold to nickel was observed. Patients with the strongest reactions to 1- and 2-euro coins showed positive responses to the lowest nickel concentrations.

The nickel content in euro coins represents a possible health hazard, especially for highly nickel-sensitive subjects. We recommend that nickel sulfate patch tests should be performed at different concentrations to determine sensitization thresholds at least in individuals with occupational exposure to coins.