Sterling silver is 92.5% pure silver and another metal, most always copper is used to make up the remaining 7.5 percent content of a sterling silver mix. Copper makes the silver harder, but gives it a tendency to tarnish.Tarnish is caused when your jewelry comes into contact with sulfur compounds, mainly hydrogen sulfide in the air. Other culprits that will cause tarnish are wool, felt, fossil fuels, rubber bands, latex gloves, rubber carpet padding, some paints and stains, and foods (eggs and onions and foods made with them). Tarnish formation is stronger in a humid climate, which is why why if you are at the beach your jewelry may tarnish much more quickly.
Store sterling silver jewelry in ziploc plastic bag. It will protect it from tarnishing
Add a small strip of anti-tarnish paper in your plastic bag to provide additional protection against tarnish. (I have them available if you need them)
Don't wrap silver in any type of tape, it can leave a sticky residue that is hard to get off.
Don't use rubber bands when storing silver, as they contain sulfur and that will react with the silver by leaving black marks that are extremely difficult to remove. Strong black tarnish marks are a bear to remove.
Keep your silver jewelry away from salt, bleach and other strong chemicals, it can corrode or tarnish it.
Don't use toothpast to polish your jewelry. It often contains baking soda which is an abrasive and will scratch your jewelry. This might be ok if your finish is a scratch finish, but if you have a highly polished piece, it will be damaged. Your best bet is to use a silver polishing cloth. If you have a piece with patina on it ("antiqued" or darkened places) the cloth will get the highlights and leave the patina. A silver dip will take it all off and you jewelry will look quite different.
Silver plated jewelry components are electroplated, with a thin coating of silver that is chemically deposited on base metal- a layer of silver so thin that it can quickly wear off with use. Many people that have problems with earrings and silver, have found that it is the nickel used in these inexpensive findings that are the problem. Always ask to be sure you are getting sterling or fine silver in your earring and necklace components, anything that touches the skin is subject to corrosives in the air and oils and acids in your skin.
Silver prices keep going up, now 650% higher (no not a typo!!) than when I started making jewelry in the late 90's, so take care of your jewelry and it will last a very long time!