It happened once. Another dog came at yours, and now every dog on the pavement gets barked at or lunged at before you have even seen them.
You are not imagining the connection. One frightening event can change how a dog reads every dog that comes after it.
Why one attack can do this
Your dog learned something in a few seconds that would normally take months. Other dogs mean danger now, and barking and lunging are an attempt to make the danger go away.
This is fear, not defiance. From your dog's point of view it works: the other dog leaves, or you do. So the behaviour gets rehearsed on the next walk.
This one goes to a professional
We route this out on purpose. Fear-based reactivity after an attack needs eyes on your dog, in your street, at your distances, and no article can do that.
Contact a qualified behaviour professional now if your dog has growled, snapped or bitten at any point since the attack.
Contact one now if you cannot reliably create distance on your walks, because every safe plan depends on distance you can actually get.
See your veterinarian first. Sudden behaviour change warrants a veterinary examination, and an injury from the attack may still be sore.
Ask any professional you speak to what they do when a dog reacts. If the answer involves a correction, a check or a collar, keep looking.
What is safe to do in the meantime
Create distance, every time. Cross the road, turn into a driveway, put a parked car between you. Distance is management, not failure.
Stop making your dog face other dogs. Holding them there until they get over it floods a frightened dog, and it usually makes the fear worse.
Work below the level at which your dog reacts. Working below the threshold at which a dog reacts is the condition for learning near a trigger.
Pay for noticing. When your dog sees a dog at a distance they can handle and turns back to you, feed them, generously.
Walk somewhere quiet for a few weeks. A lane at 7am beats the park at 5pm while you wait for an appointment.
Do not add punishment to fear
A correction, a leash check or an aversive collar may stop the barking in the moment. Punishment-based approaches are associated with fear, avoidance and defensive aggression, and your dog is already frightened.
Reward-based methods are what is recommended for behaviour change, and behaviour change is built from management plus reinforcement together. That is as true after an attack as before one.
Safety note
Get help now if your dog has growled, snapped or bitten a person or another dog since the attack. The same applies if you cannot keep both dogs safe on a walk. Speak to your veterinarian and to a qualified behaviour professional before you change anything else. Sudden behaviour change warrants a veterinary examination, and any wound from the attack needs checking.
We are not going to promise you the dog you had before. Plenty of dogs become comfortable enough to walk past other dogs calmly, and that work starts with distance and help.
Today's version, in one line: walk somewhere quiet, keep the distance your dog can manage, and book a qualified behaviour professional.