Knife Ruby

Bobby on Supernatural (spoilers new season)?

Okay. I get that Bobby killed the demon inside of him in the first episode of season five, though I don’t know why he wouldn’t have the same tattoos that Dean and Sam have. Anyway, why didn’t he die? I looked up information on Ruby’s knife and the general concesus is that once stabbed both the victim and the demon die. So….why didn’t Bobby die?

The knife is not special for the host, only the demon. That is, it always kills the demon, but only injures the host in the same way it would as if it were just a normal knife.

Boiler Room #10 Playing with Knives (Ruby)