Unfortunately, brass is not hypoallergenic. It can cause allergic reactions because of the copper and zinc it contains. The copper can turn your skin green, but it is not as toxic as other materials. It only means that your skin’s moisture is reacting with the metal. If you are still considering buying brass jewelry, there are simple ways to prevent your skin from turning green. You can apply a thin coat of clear nail polish to prevent the metal from reacting with your skin.