Tests done on coins reveal that most of them have small amounts of dirt and bacteria that are too low to cause people any harm. The metal in coins acts as a natural barrier to the growth of bacteria, which require ideal surfaces and temperatures to thrive. In one test, low levels of the staphylococcus bacteria were found around the edges of coins that had sat inside of purses.
Coins minted in the United States have a built-in safeguard that protects the public from germs. Each coin has a percentage of copper as part of its metal makeup. Copper has natural antibacterial properties, which makes it ideal for producing money. Half-dollars, quarters and dimes have the highest amounts of copper at 91.67 percent. Dollar coins have slightly less. Nickels are made of 75 percent copper. Pennies are mostly zinc with a small copper lining added.
While washing coins is not recommended, there may be some instances that require a gentle cleaning. To clean coins, fill a plastic container with warm water, and add a small amount of dish soap. Place the coins into the container and gently rub each coin between the fingers to remove debris. Rinse coins in a second container of distilled water, and let them air dry.