This article is from the Piercing FAQ, by Anne Greenblatt with numerous contributions by others.
Sterling silver is 92.5% silver alloyed with copper or some other
metal. Sterling silver jewelry is usually marked "925."
While silver and sterling silver jewelry can often be safely worn in
healed piercings, neither should be worn in a new or unhealed piercing
or in a piercing that is located in a moist area of the body such as
the mouth or genitals.
Silver tarnishes quickly. When worn in a new piercing, the tarnish can
be deposited into the skin causing it to darken or turn grey, often
permanently.
Silver is very soft and is easily scratched. Scratches in the jewelry
surface can easily irritate even a healed piercing and trap bacteria,
encouraging infection.
 
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