The premise behind the Gentle Leader (at least what I was taught) is that when fitted properly, it sits right behind the occipital bone, putting pressure on a spot that is supposed to be calming. I know a dog that it worked wonders for *in the house*. I wouldn't use one on a reactive dog for just the reasons stated above. Too much neck snapping for me. But if it keeps them calm in the house, or enough that you can teach new things, then it's all good.