Rough drawing of dog wearing a head collar
"Does your dog bite?"
"No, he's wearing a Halti, to keep him from pulling on the leash!"
The head collar, commonly of the Halti or Gentle Leader variety, is not a device to keep a dog from biting. It's a special type of collar designed to keep a dog from that activity most dogs love so well--and that has dog owners massaging sore shoulders. A head collar can keep your dog from pulling on the lead while you have time to train him not to do so.
Haltis and Gentle Leaders work similarly to a horse's halter. They are worn on the face while the lease attaches to a ring at the neck. The dog is guided gently by the head instead of having the option to pull at the neck or chest as with a standard collar or harness.
Due to the fact that the head halter is "self correcting"--it causes your dog to adjust his movement in the direction that you want him to go, without force--it is a gentle, less harsh form of control than a choke or pinch collar. It does not work like a muzzle does--you dog can still eat, drink, pant, and do everything she normally does without the head collar. But never leave your dog unattended while he's wearing one.
This type of collar should never be used with a retractable leash, which could severely jerk your dog's neck and cause serious injury.
Both Gentle Leaders and Haltis are carried in many pet supply stores. While you may need some initial assistance in fitting and attaching the collar the first time around, they are easy to use and generally come with ample instructions.
However, as with many other elements of dog care and training, it is absolutely critical to your satisfaction and your dog's to exercise patience in getting your dog accustomed to this type of collar. They generally don't like it at first and you want to follow the standard practice of introducing briefly, treat, remove, reintroduce and gradually work up to longer periods.
And remember--always work with an upbeat attitude so your dog knows it's a good thing--and you will too!