i have read about it, heard about it and now i have unfortunately seen where a collar grew into the dog's neck. This dog ws at the humane society. The owner was horrified, when she discovered this she took the dog straight to the er vet (we know that is a huge expense) and was doing a follow up at the humane society. the neck had a half inch patch of missing sking all around the neck. Please if you have never owned a dog before check your collars regularly..you should be able to slip two or three fingers inbetween the collar and the neck. It made my stomach feel like it was full of pins and needles to see that..i cannot imagine the discomfort involved. Also how a pet owner could not see..surely there is scratching or rubbing but i do not know for sure since i have never seen this happen. At our kennel collars were not only carfully monitored, but on puppies they were checked several times a week. At another kennel there were no collars allowed on the dogs while in the run. I take the collars off my dogs when they are in for sure and not going out soon..Vic's comes off with the leash because his skin is so soft and pink..and not a whole lot of hair there, i don't want anything to rub off what he does have.