Nickel is an inexpensive metal that resists tarnishing and gives the appearance of silver and other more expensive metals. Nickel does have some problems, however. Many people are allergic to the metal, which can cause rashes and other problems, and nickel will tarnish over time, especially if exposed to moisture. It you treat nickel properly, it is possible to avoid many of its pitfalls. People who have only minor allergies to the metal may find they can still wear nickel when it's treated properly.
Create a cleaner consisting of one-part vinegar and one-part water. Dip a soft cloth into the mixture and clean the metal with the mixture to remove any existing contaminants.
Make a paste from baking soda and water and rub it onto the jewelry with a soft cloth to remove any existing tarnish spots. You can also use silver polish to remove tarnish, but this may aggravate allergies for some people.
Rinse the nickel with a damp cloth and allow the jewelry to dry completely.
Place a small amount of a polymer car polish onto a soft cloth. Rub the polish over the jewelry. Allow the polish to sit on the jewelry for about five minutes, then buff off any excess polish. This will coat the metal in a polymer finish that will harden and protect the metal from exposure to moisture and air, which can cause tarnishing. The polymer coating will also protect the nickel from coming in direct contact with the skin.
If the polymer coating is not thick enough to prevent your metal sensitivity, you can paint an epoxy resin coating over the nickel. This coating will completely coat the nickel with a hard finish and block the metal from coming in contact with the skin.