Leash aggression or reactivity is one of most common "problem" behaviours that dog trainers are contacted to help with everyday.
Many people are dealing with high anxiety and stress around their dogs behaviour on walks. Just the thought of taking their dog out for their daily walk creates an ache in their stomach and starts the mental whirlwind of worry.
Some people get up at 4am to walk their dog so they won't encounter anyone else, some people hide behind bushes or cars to avoid oncoming dogs, and some people avoid walking their dogs at all because they simply cannot handle the stress.
You're not alone!
The good news is that it is trainable and can get better! The bad news is that it doesn't usually happen overnight.
Most dogs with leash reactivity are having a fearful reaction. They are typically afraid, insecure, and under-socialized. It's not possible to eradicate that fear or anxiety your dog is having overnight. You can, however, reduce the amount of stress your dog is under through desensitization and giving them clear expectations and boundaries, and an alternative behaviour (such as ignoring and walking calmly).
Where to start:
On the Walk:
When you encounter another dog (Some things you can try. All dogs are different so give them a try and see what helps):
I don't believe it's an overnight fix for most dogs, though some respond immediately to a trainer with great timing and consistency!
Remember that your dog's behaviour on the walk starts in the home. Make sure you have established leadership at home and that will help your dog trust that you can handle whatever pops up during your walks.