Do microchips contain nickel?

I have a foster cat who is allergic to nickel. He has to be microchipped and I'm not sure if the chip contains any nickel. I know it contains copper and I'm pretty sure that there is no nickel in copper but I want to be sure that there is no nickel in the chip elsewhere. Does anyone know?

I have no idea. If you know what type of chip it is, perhaps contact the company and ask them the question directly?

I believe it is all encased in glass or plastic.