Dog leash aggression is caused by the removal of a dogs escape route.
If you think about it, a normal reaction of both humans and dogs when they see potential danger is either to stand up and fight or run.
When a dog is put on a leash its option to run is removed and so if it perceives another dog or human as potentially dangerous it may well show aggressive behavior such as growling, barking and lunging.
Some relatively easy going dogs are totally different once on a leash.
Dealing with Leash Aggression First find out what causes the leash aggression, this could be al or specific dogs, all people or certain people eg.
Men, children, people in hats etc etc.
Once you know what causes the reaction you can try and desensitize your dog to it.
For example if your dog becomes aggressive when walking on the leash near other dogs, the next time you are approaching one walk round it in a large semi circle so you are always a few metres away.
You will know if you are still too close if your dog reacts by barking, growling or lunging.
Once you have found a distance where your dog is comfortable keep doing this every time you pass dogs and praise and give it a treat if it doesn't react.
If there isn't room to make a semi circle round the other dog you can either turn round and walk in the opposite direction or try running quickly past.
Once you have practiced and your dog no longer reacts at this distance start making the semi circle smaller so you are not so far away.
If your dog reacts you have gone too close and need to go back a step.
If you can enlist the help of someone with an easy going dog who is prepared to help this can speed up your progress.
Other Techniques to help with leash aggression Distraction is another way you can help to stop leash aggression this can be done by rapidly feeding treats as you walk past the other dog, distracting with a treat or toy or asking your dog to perform a task/trick.
You can also teach your dog to make eye contact with you so it looks at you rather than the thing it reacts to.
You can do this by moving a treat up to your face near your eyes and adding a command such as "look at me" once the dog looks give it a treat.
Practice this, but gradually stop holding the treat still pointing at your eyes and saying look at me then again give it a treat.
Once the dog is confidently doing this every time practice outside and then try it when other distractions are about when you dog is on leash.
A clicker can also be a useful aid to help deal with leash aggression.
Once you have taught your dog that the clicker means good and a treat is on the way you can use this as an aid when out leash walking.
As you walk past another dog or person and your dog doesn't react click and treat.
A head collar may also be worth considering.
Although it may take your dog a little time to get used to wearing a head collar it gives you the benefit that you can turn its head away from the thing it normally acts aggressive towards.
A head collar also makes it very difficult for a dog to pull on the leash.
If you have a strong dog who is leash aggressive you may well be anticipating the aggression knowing that you need to brace yourself to hold on to it.
The head collar means you don't have to worry about this as much and as you relax it should help your dog to relax too.