The wire on the left is silver-filled (much thicker layer of sterling) and the wire on the right is silver-plated. Because of it’s extra thin coating, the silver on silver-plated metals can wear off over time, causing the base metal to show. It is the base metal (often unprotected copper) that causes allergic reactions sometimes when plating wears thin.
This does not happen with silver-filled metals. The bonded layer is thick enough to withstand small nicks, and it will never wear off. If you are allergic to silver-plate but are able to wear sterling silver, you should also be able to wear silver-filled without causing an allergic reaction. Blessed Art uses a blend of silver which is 90% brass (core) and has an outside layer which is 10% sterling silver.
Silver filled is a wonderful midway product that allows buyers to have the shine of silver without the full price!