Nickel is a metal which is commonly used as a binding metal in jewellery, metal fastenings on clothings such as zips and buttons, cutlery and mobile phone casings.
Silver coins contain traces of nickel, occupational allergic dermatitis is common in people who work frequently with cash.
Nickel allergy has also been noted after transplantation surgery, mostly associated with hip and knee replacements and in dental procedures.
Nickel can also be found in foods if cooked with nickel plated cookware and traces are found in canned foods.
I have put together some more comprehensive resources at http://www.allergyresources.co.uk/Nickel.php
The allergy resources page for nickel covers the key allergens, which allergic syndromes are linked to this allergy and other foods which are commonly cross reactive with nickel.
There is also regularly updated links to useful websites specifically for nickel allergies and the latest research papers on the topic.
If you have multiple allergies and are interested in how they are linked or want to find out more about food allergies outside the usual top 14 then you can follow me on Facebook or Twitter, where I share a food allergy card every day of the week.