Swiss scientists have revealed just how allergenic the euro coins are to those suffering from nickel allergy, a relatively common syndrome.
This hand is in danger of going all red and itchy.
Worried Wolfgang, rattling his loose change in his pockets as he waits for the tram; bored Beatrice, absent-mindedly making piles of euros on her desk; hungry Henri, running off to the pastry shop with coins clutched in his sweaty little fists - all are playing a dangerous game.
According to a team of Swiss scientists, some of us in the eurozone who spend time handling the single currency are in danger of a nasty shock.
Following a study earlier this year by Swedish and British scientists into the link between the euro coins and eczema, further information from Switzerland links the coins to allergic reactions.
The euro currency, adopted by most of Europe at the beginning of this year, can release up to 320 times the amount of nickel that European Union regulations say triggers skin reactions in people allergic to the metal.
Euro coins in breach of safe nickel regulations
A French newspaper seller sorts out his stock of change in euro coins.
The EU directive states legal limits for the amount of nickel released by items that are normally in prolonged contact with the skin, such as earrings or watches. It is not routinely used to test coins
The results show the highest rates of nickel release ever measured for any coins. Frank Nestle of the University of Zurich, writing in the science magazine, Nature, says he and his colleagues have now worked out why - and it's not just that the new coins contain too much nickel.
Human sweat acts as a conductor, releasing irritant
In a sweaty palm, each coin is like a tiny battery, according to Nestle's team. When sweat gets between the two different alloys of the central pill and outer ring of 1 and 2 euro pieces, metal ions flow between them. This makes the coins corrode, releasing nickel ions, which can set off itching and redness in up to 30 per cent of the population.
Nickel is the most important allergen in the environment because of the frequency with which people come into contact with it. Nickel is common in jewellery, coins and clothing such as jean studs.
The researchers at the University of Zurich's dermatology department conducted tests where both types of coin were taped to the skin of seven volunteers known to suffer nickel allergies. The volunteers experienced redness of the skin and the formation of vesicles, blisters like those seen in chicken pox.
Prolonged exposure results in corrosion of coins
Discovering the link the reaction between coin and skin, the scientists suspended a one-euro coin in 'artificial human sweat'. It turned brown and began to erode.
But findings were not as disastrous as one would first think. It would only provide an increased danger if the coin was held tightly in a human hand for 36 hours, the duration of the test.
Dermatologists have been lobbying the EU for many years to reduce nickel exposure. But the success gained from the EU nickel directive was not repeated with the euro coins.
German Chancellor Gerhard Schroeder takes no risks and keeps his euro coins in quarantine.
Lower-value euro coins are made of nickel-free alloys. Many countries wanted all the new euro coins to be nickel free.
"There are advantages to putting nickel into coins," explains Nestle's colleague Hannes Speidel in the Nature article. Nickel is magnetic, which helps vending machines to identify the coins. Using two alloys also makes the 1 and 2 euro coins harder to counterfeit.
Even for people with nickel allergies, the coins will not pose huge health risks. The most common reaction is red, sore skin, a mild annoyance for those, like shopkeepers and bank clerks, who handle lots of money.