Certain metallic elements, when in prolonged contact with skin, can produce a greenish discoloration. This occurs due to a chemical reaction between the metal, perspiration, and other substances on the skin’s surface. For example, jewelry containing copper is often associated with this effect.
The phenomenon is generally harmless and poses no significant health risk. Historically, the presence of green staining from jewelry served as an indicator of the metal’s composition, highlighting the use of alloys containing reactive metals. While not dangerous, this discoloration can be aesthetically undesirable for some individuals.