Inflation is the rate at which the general level of prices for goods and services is rising and, consequently, the purchasing power of currency is falling. Central banks attempt to limit inflation, and avoid deflation, in order to keep the economy running smoothly. Next Up.
If you are not allergic to metal, the reason for this reaction is chemical. It's due to a combination of the metal and the acids in your skin. Experts say that there are several metals that oxidize with your skin to give you a noticeable green ring around your finger. A ring made of copper is a common culprit, but even silver and gold metals can cause discoloration.
Then would could try a wire brush and some brasso........I think the green is caused by the corrosion of the copper in the brass. Go easy with the wire brush though, it may leave unwanted scratches in the brass if you brush too hard.