[Yokuutsu]

If people have an allergy, it's to the nickel in the metal (more than likely)

It's kind why people argue about what should be used in new piercings-titanium steel (I think) or surgical steel.

But even without an allergy piercings can do that...it just depends on the person and how they were done....and if the person tosses and turns or rubs it alot...