It is a common misconception that a green ring around your neck, wrist or finger is caused by an allergic reaction to the metals in your jewelry. Though it is true that some people are allergic to metals like nickel and copper, that green ring is usually caused when metals rub off onto the skin. This is more likely to happen in areas where we sweat the most, like the palms of our hands and the backs of our necks.
Does a ring discolor your finger? Apply clear nail polish to the inside of the band. This will act as a barrier between your skin and the metal while locking the metals into place. Try this on inexpensive costume jewelry that may be fun to wear, but hard to clean.