Invisible Woman
Senior Member (Voting Rights)
tried the safety pin test several times, no reaction.
It also might depend how and where you placed it.
It might bring need to be in very close contact with your skin for the whole time you wear it rather than just brush against it.
As others have mentioned, where you place it might be important - maybe taping it to your skin under the waistband of your trousers might produce a reaction where simply being pinned to the inside of a tee shirt, especially if that tee shirt isn't a really snug fit, won't.
Also worth double checking the safety pin you use is nickel coated - I think most of them are.