The reason that some copper turns green on itself or on skin is, that there is a chemical reaction. Copper when exposed to acids and high humidity, be it in the air or on the body will cause this reaction.
Many feel, that there is a therapeutic health benefit to wearing copper bracelets or copper jewellery that touches the skin. People have been wearing copper for centuries. It has been documented in artworks and found objects that were entombed with the ancients.
How does one minimize this reaction? Many individuals will coat the copper item with lacquer. A coating of Clear nail polish works well for jewellery. It is inexpensive and readily available.
Others, will wash the copper jewellery frequently with soap and water OR immerse in a potion of salt and lemon juice for a brightening treatment.
Copper is one of natures’ wonders.