Walking on a collar alone does not cause CT -- but it CAN aggravate CT for a dog who already has it.  In the grand scheme of things, a dog that is not pulling, and is walked on a collar isn't THAT bad.  I do use slip collars for quick pee trips outside when he doesn't have a harness on and I don't feel like dealing with it.   
However, I prefer harnesses for multiple reasons but do understand why trainers prefer collars at times.  Most trainers know dogs have been taught to pull on harnesses - think sled dogs.  However, I believe a dog can just as easily be trained to not pull on a harness.  Jackson is 18lbs and wears a harness.  I like being able to easily lift him into my arms out of potential danger, it also just seems more comfortable, I worry less about yanking by accident, etc.  I just prefer harnesses.        |