There can be a number of different reasons why a dog will bite on his or her leash. Most of those reasons are because the dog is either resisting you and your control or simply wanting to play. No matter which, it is annoying and must be stopped if you want to train your dog to walk nicely on leash.
The methods that I discuss below deal with making the leash taste bad so that your dog finds it undesirable to have it in the mouth. Of course keep in mind that patience is important while eliminating this habit.
If your dog has already started this annoying habit then you will need to do some behavior modification to eliminate the problem. The first method that I always suggest is to soak the lower 18 inches or so of the leash with bitter apple. Bitter apple is a spray that is available at all the pet stores and will deter you dog because of its bad taste.
If that does not work then I suggest you soak the lower 18 inches of the leash with lemon juice. It seems that most dogs do not like the taste and will quit putting the leash in their mouth to avoid the taste.
Of course there is always that hard core dog that does not seemed to be bothered by either bitter apple or the lemon juice so we move on to my third option which is hot. Yes you want to purchase a hot sauce like tabasco, Cholula, or any other hot sauce that comes in a bottle and is available at all grocery stores usually where they have the Mexican foods and spices.
One way to avoid this problem all together is to start training your dog to tolerate the leash and enjoy going for walk early while it is still a young puppy. It seems the longer you wait to introduce the leash the worse the problem actually is.
There is no better way to establish a good pack leader attitude for your dog than going for walks. Taking the time to teach your dog to walk nicely at your side and not mouthing or pulling on the leash is something that will be rewarded with many great enjoyable walks. Walking your dog develops the dog master relationship and it is something that your dog will thank you for many times over the years.