The amount of nickel is regulated in European products that come into direct and prolonged contact with human skin¹ because this metal may cause contact allergy, particularly hand eczema^{2, 3, 4}. Here we show that 1- and 2-euro coins induce positive skin-test reactions in sensitized individuals and release 240–320-fold more nickel than is allowed under the European Union Nickel Directive. A factor contributing to this high release of nickel is corrosion due to the bimetallic structure of these coins, which generates a galvanic potential of 30–40 mV in human sweat.

1. Department of Dermatology, University of Zürich Hospital, Zürich 8901, Switzerland
   e-mail: Email: nestle@derm.unizh.ch
2. Institute of Metallurgy, Department of Materials, ETH Zürich, Zürich 8092, Switzerland