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Protecting against nickel allergies

Thursday, 26 November 2015

We all know about allergies to various types of food and allergies to things in the air that we inhale, but there is also a class of allergies pertaining to things we touch. These are known as "contact allergies" and the most common of them is an allergy to nickel, which bodes ill for the copper bracelet and magnetic jewellery industry.

The reason for this is that the skin absorbs nickel ions (charged atoms that have lost one or two of their outer electrons). The amount of absorption, and the extent that it affects people, varies from one individual to another. But one thing is universally agreed: it is a problem. And the reason that nickel is a problem to anyone with such an allergy, is because nickel is widely used in jewellery.

Now you might think that the simple solution to all of this would be to ban it from use in jewellery altogether. However, there is a problem here. Because Nickel has many good properties that make it ideally suited to jewellery. For example when applied as a coating, nickel creates a much smoother surface than most other metals, in a process known as "levelling". Nickel is also very bright and can make gold and silver even more lustrous than they normally appear. That is why gold jewellery shines - or perhaps I should say "glisters", to borrow a word from Shakespeare - more than gold bullion.

And in the case of silver, nickel also prevents tarnishing, something that would otherwise be a big problem - especially in jewellery which by its nature tends to be handled a lot. Similarly, when applied to copper jewellery, nickel prevents the copper atoms from migrating to the surface. This is important, because copper has a tendency to react with the oxygen in the atmosphere, leading to the formation of copper oxide. This oxidization is bad for jewellery not only because it turns the surface an ugly green - which undermines the very aesthetic qualities that are the raison d'etre for jewellery - but also because it makes the surface rough, and thus uncomfortable to the skin and unsuitable to wear!

Aside from its use as a surface coating agent, nickel may also be used as an alloying agent, again in jewellery. Gold, silver and even platinum may be alloyed with nickel to change not only the appearance of the precious metal, but also its tensile strength and hardness. Gold, for example, is actually quite soft. Consequently, pure gold jewellery can be easily deformed or misshapen. But add a little bit of nickel to the gold and WHAM - all of a sudden, it's a lot stronger and harder! It also looks different, essentially becoming white gold, which could easily be mistaken for platinum!

Now there are products other than nickel that could perform some if not all of these functions, most notably palladium - the only metal with a complete outer electron shell, to the physicists and chemists among you. But palladium is expensive: indeed it is a precious metal. A quick glance at the spot prices on the London Metal Exchange shows that palladium currently costs forty times as much as silver and half the price of gold - almost up there with rhodium and platinum!

Thus, it is easy to see why the industry is reluctant to adopt it for, say, clothing fasteners. And even for jewellery, it is important to remember that not all jewellery is expensive. Aside from the luxury jewellery made from precious stones and precious metals, there are at least two other classes of jewellery. One is, of course, Costume Jewellery, that seeks to mimic its expensive counterpart, using glass or garnet stones and metal alloys - notably containing nickel. The other is jewellery that simply aims to be aesthetically pleasing without breaking the bank. I include therapeutic copper bracelets and magnetic bracelets in this latter category.

So getting rid of  the nickel in jewellery is simply not an option. But what, then, can be done to address the issue of human allergies to it?

Well it turns out that just as not all people are affected by contact with nickel in the same way (or to the same extent), not all nickel products have the same rate of transfer of the nickel ions to (or through) the skin. So the government very sensibly enacted legislation that placed a limit on the permissible rate at which nickel could be released when it came into direct contact with human skin. This law applied not only to jewellery but to any nickel product that might come into contact with people, such as fasteners on women's dresses, etc.

However, there is no point having a law unless there are also means of enforcement and also the practical possibility of compliance. Both of these are provided by the existence of nickel testing services (such as the Sheffield Assay Office and the testing laboratory of the Goldsmith's Company) that can test products for their nickel transfer rate. At first this might seem problematical, given that the law stipulates the maximum permissible transfer rate over a two-year period. But these clever testing services have developed procedures that simulate the two-year time-frame and can thus test jewellery containing nickel in a much shorter time-scale.

These are the kind of services that governments use to monitor compliance. They are also the kind of services that ethical and responsible suppliers of products containing nickel use to monitor their own compliance. Now obviously, the suppliers cannot test all their products, as it is a destructive test. That would like striking every match in the box to make sure that they all work! However, what they can do - and what responsible suppliers of jewellery actually do - is test a fair sample of randomly selected items.

Of course, not all suppliers of such products comply with their legal obligations. The sad fact is that not all suppliers are ethical in their outlook. But one that is ethical and fully compliant with the law is Magnetic Therapy Bracelets. When you buy a bracelet containing nickel from them, you can be sure that it complies with the law and that the nickel transfer rate is within the safety level set by  BS EN 1811:2011 and BS EN 12472 as well as EC Nickel Directive 1907/2006 REACH Annex XVII, Item 27.