Yes, they can, both dog trainers we consulted told The Spruce Pets. “This is why I always recommend a well-fitted harness. If a dog pulls on leash and is only wearing a collar, they can do a lot of damage to the neck or spine,” Gianella says. “I also like to do a lot of training where I am reinforcing them when there is a loose leash, when there is no tension on the leash or when they are by my side.” Many trainers will recommend using front-clip harnesses that will turn dogs around when they pull on the leash. Sunny likes “Y-shaped" harnesses that don't inhibit the dog's range of motion.  “Dogs can hurt themselves pulling on a leash and this can happen even more easily when they are pulling while being walked on a slip collar, flat collar, or a slip lead,” Sunny says. “Constant pressure on a dog's neck can be painful and dangerous and could even potentially lead to a collapsed trachea.”