What kind of rash is this under my watch, and how can I get rid of it?

Nickel allergy. Nickel allergy can affect people of all ages. A nickel allergy usually develops after repeated or prolonged exposure to items containing nickel. Treatments can reduce the symptoms of nickel allergy. Once you develop nickel allergy, however, you will always be sensitive to the metal and should avoid contact. Nickel can be in earrings, necklaces, watches, and other metal products.