no they are not dangerious to the dog..

spiked collars were originally ment to stop ppl from trust passing in court yards. When ppl tryed to stop attack dogs from biting them they would grab for the scruff, or neck of the animal. with a spiked *or screwed* collar around the dogs neck the person would get cut..

they used to make spiked collars with rusted screws. they have a bad past lol