of collars can aid in stopping a strong dog from pulling an owner in an unsafe direction. They are also recommended for dogs that pull as the pressure will no longer be directly on their wind pipe. The theory behind the utility of head halters is that if you have control of the head, you have control of the body. The head collar generally consists of two loops, one behind the ears and the other over the nose. This tool generally makes it more difficult for the dog to pull on its leash. This is a management tool only, it does not train the dog not to pull. Controversy Supporters of the head halter say that it enables the handler to control the dog's head, and makes the dog unable to pull using its full strength. They claim it is especially useful with reactive dogs, where control of the dog's head can be a safety issue. Those who do not recommend use of the head halter say that some dogs find it unnatural and uncomfortable. If the collar is too tight, it may dig too deeply into the skin or the strap around the muzzle may push into the dog's eyes. Cervical injury is a possible result from improper use of the head halter; if a dog is jerked suddenly by the leash attached to the head halter, the dog's nose is pulled sharply to the side, which might result in neck injury. If the nose strap is fitted too tightly, the hair on the muzzle can also be rubbed off, or the dog might paw and scratch at its face, causing injuries ranging from mere bare skin to severe abrasions. Some head halters such as the Canny Collar attach behind the neck and tighten around the nose when the dog pulls to deter the dog from pulling. Manufacturers claim they are safer than halters that attach below the muzzle because they do not pull the dog's head to one side, avoiding stress on the neck area. Some rear-fastening head halters can have the noseband removed during use, therefore providing an element of training the dog to eventually walk on a regular collar and lead. Aversive collars Aversive collars use levels of discomfort or an unpleasant sensation to encourage a dog to modify unwanted behaviors. The use of aversive collars is controversial, with some humane and veterinary organizations recommending against