The weird colors that can form around your finger (or on ears, or wrists, or neck!) after removing a piece of jewelry is caused by a chemical reaction between the acids in your skin (or lotions on your skin) and various metals.
There are several metals that oxidize or react with skin and then cause discoloration. Copper is a reactive metal that can leave a greenish hue on skin. Some jewelry is made of pure copper, and other jewelry is made from metals that are alloyed (or mixed) with copper. Sterling Silver is 92.5% pure silver and 7.5% copper.
So yes, Sterling Silver jewelry, including rings, can turn your skin green. So can yellow gold jewelry!
Silver plated jewelry can be any underlying metal, but is plated with pure silver. This plated jewelry can cause tarnish to form on your skin! This would leave a dark grey or black discoloration.
No worries though---these weird colors are totally harmless and can easily wash off, or can be removed by using a little nail polish remover or even makeup remover.
Nickel is used in jewelry and can result in a red, itchy "ring" around the finger, or wherever it touches the skin. A lot of people are sensitive, or allergic, to nickel.
How To Avoid "Ring Around The Finger"
Even gold jewelry, as well as silver, can cause discoloration on skin. Yellow gold is also alloyed with copper. So avoiding "cheap" jewelry isn't always the answer!
Stainless Steel jewelry is a good choice for very sensitive skin. Rhodium and Platinum also are considered hypoallergenic. All white gold jewelry, and often Sterling Silver jewelry, is plated with Rhodium, so these are good choices.
Also, avoid getting soap, lotions, chlorine and household chemicals (like ammonia) near your jewelry. Remove your jewelry before swimming (especially saltwater) or doing dishes or bathing.
Some people apply clear nail polish to the inside of their Sterling Silver rings. Applying some sort of barrier does help!
So if you buy a piece of jewelry that is Sterling Silver, and it turns your skin colors, now you know that it's not because the sterling is "fake". It's because the silver is reacting with your skin and environment!
