Too many metals are alloyed with nickel – this gives them extra strength but gives the potential for causing or excacerbating a nickel allergy. Even gold often contains nickel – higher karat numbers imply fewer impurities in the gold. “Impurities” in the case of gold simply means other metals alloyed with the gold.
The impurities make the gold stronger and more hard wearing and may be used to change it’s color but give the potential for quantities of nickel in continuous contact with the skin (via a ring, necklace, earrings, watch, etc).
However the important factor is not actually total nickel content but whether the nickel is “free” – ie is soluble in sweat or other liquids. It the nickel is chemically bonded such that it won’t come out, it is much less likely to cause a problem.
Nickel test kits
You can find out whether an item has free nickel by using a nickel test kit. Test kits are multi-use, inexpensive, easy to use and can be used to test any metal item with enough surface area to rub the test on. Use it on jewelry, tools, watches, buttons, zippers, coins, etc.
The kits are very simple to use – there is one premixed solution which you drop on to (eg) a cotton bud – a few drops.
Then rub the wetted end of the cotton bud on the item in question… if free nickel is present, the tip will turn red.