If you do want to try a head halter to train your dog not to pull and tug, or to keep her away from dogs and people in order to prevent altercations, it’s imperative that it fit right — both for her comfort and to work properly.
A head halter most often comes with two soft, adjustable nylon straps. One goes around the nose (which is why a head halter is not for a brachycephalic dog, which has a very short nose), and the other rides high on the neck, just behind the ears (in front of the throat collar rather than under it).
The neck strap should be kept snug, with barely enough room to fit your pinky under it. The nose strap, on the other hand, which sits at the base of the muzzle — close to the dog’s eyes — should be kept loose enough so that the dog can eat, drink, or pant with it on.
It’s believed that the head halter works by perhaps mimicking the pressure a mother dog might apply to areas that are innately sensitized to receive signals to relax and go limp. When you gently pull upward on the leash, the neck strap tenses, and that might deliver a message like the one a puppy’s mother sends when she picks up her charge gently by the scruff of her neck to remove her from something. The puppy instinctively takes it easy and accepts being led.
Same for the gentle pressure exerted around the muzzle via the nose band. It perhaps reminds a dog of her mother’s touch. No jerking of a collar or pain is involved.