I’m the big wet blanket that doesn’t like them, them meaning the semi-vast number of canine “head halters”–well, me and a lot of dog trainers. My principal concern is health; the best way for me to describe it is to tell you to do it to yourself. Put your hand under your chin where the leash attaches to the head halter and push up and to the side, the way the pressure of the leash pulls the dog’s head. Doesn’t feel all that great, does it? You want to stop almost immediately, and you’d probably be more than a little freaked out if someone had the power to keep torquing it beyond where you are comfortable.
The head halter literature continually talks about it being like a horse halter, just like horses are led. But it’s not. In order to duplicate the action of the dog head harness on a horse, you’d be putting the lead rope of the horse through a ring in the ceiling and then pulling the rope–which would immediately be labeled insane.
If you want to use a head halter, the action must be to bring the head down to the chest, with almost no lateral movement. That’s the way you lead a horse. I could do that on my Danes, because their heads were at my waist height, and I did own a GL that I used on the rare occasions that I had to take a dog to a location where I anticipated the dog pulling but I didn’t want to use a prong collar (for example, when we went to a street fair and I didn’t want anyone thinking that prong collar = dangerous dog). On a cocker spaniel, keeping the head motion low would require you to be lying on the ground.
In terms of training–I am not a professional. But I can tell you that the dogs I see behaving the very worst when they have a collar on, just totally out of control, are usually pulling an owner behind them who is yelling “But he does so well on the halti!”
Several dog trainers I know just hate the attitude it puts the dogs in–they want happy eager workers who are jumping at the chance to obey, and putting the halter on the dog seems to depress the dog.
Remember that the goal of any dog training tool is to get rid of the tool. It should never be an end in and of itself. It is a bridge to allow you to communicate with your dog so the dog learns how to listen and understand without you having to use the tool. Far too many owners and even many trainers use tools because they physically inhibit certain bad behaviors (for example, the no-pull harnesses make it physically difficult for the dog to walk straight forward while pulling) but do not transmit your signal to the dog. There’s a reason that choke and prong collars are the most common training aids–they effectively link your hand to the dog’s brain. It’s harder to establish that link when the training aid does not change its feel on the dog according to how your hand is changing. If your dog behaves well on a prong or an EZ-pull or a GL or a fill in the blank, and pulls like a semi truck on a flat collar, you’ve inhibited the dog but not trained it.
If you can use a head halter safely with no lateral movement, the dog is happy and eager while using it, and if you are being taught how to use it in order to get rid of it (in other words, if you are being taught how to use it to develop a consistent loose-lead walk, so the dog could be on dental floss and it wouldn’t pull), then like any tool it is fine.
A note on safety: prongs are actually the least likely to ever injure your dog, even if used incorrectly. They’re even safer than flat buckle collars. Thin chokes, though in my opinion the very best communicators of your signals to the dog, are arguably the most sensitive to incorrect use. Please don’t use a thin choke unless you are being trained by a very good trainer who is teaching you exactly how, when, and where to use it. It took me months of weekly training to get to the point where I wasn’t a complete disaster with the thin choke. I couldn’t live without them now–I can use my pinky finger to tell a dog to shift its weight over and move a front foot a half-inch–but I would NEVER recommend them without a trainer.