If I remember correctly, it is (at least sometimes) used as an antiseptic isn't it? Problem is a Werewolf wouldn't realize you had it in you until after you were already Human tar tar! NOT a good thing to be.
Silver has some anti-bacterial qualities, which is why the early pioneers would put a silver dollar in their water barrels. I believe that silver is also an ingredient in some burn ointments for the same reason.
