Allergic reaction. You may be allergic to the metal nickel which is found in varying amounts in bothgold and costume jewelry. You can be allergy tested to confirm this. Wear sterling silver which does not contain nickel or hypoallergenic nickel free jewelry available fromn the chain claires.
Nickel Free. To avoid nickel (www.Nickelallergyinformation.Com) you can test your earrings or any other jewelry including cell phones for the presence of nickel with a simple color changing dimethylglyoxime nickel test. Best advice is to see a dermatologist for evaluation.