Some jewelry is marketed as "base metal" (usually nickel, or brass) and disguised with a thin coating of sterling silver, called "plating" which ultimately wears off, looks cheap and can lead to skin irritation. The problem with inexpensive metals such as nickel or brass, is that they can cause infections, especially with earrings. Other metals can turn the skin green or cause other allergic reactions and there are even unscrupulous jewelry manufacturers that use cancer-causing metals like cadmium in their jewelry. Bottom line: Sterling silver, aka 925 silver is hypoallergenic, high quality, stylish and safe.