I do know that the cocoa bean contains theobromine (I think that's the name of the toxin), and, that's what's fatal. It's different for every dog, though, as for how much they can eat before it's dangerous, but, it's obviously better just to keep it all away. I also know that the amount of theobromine differs from chocolate to chocolate....dark or plain chocolate has the highest content. And, cocoa powder is even more dangerous. As for the nose part, I'm not sure. I always thought it was just a sign of the body temperature of the dog. And, I would imagine, just as a person's body temperature changes and doesn't necessarily signal sickness, I'd guess it was the same for dogs. But, like I said, I'm not sure.