Introduction to Reactive Dogs

Dogs can be reactive for all sorts of reasons most common is due to a lack of socialization with people, dogs and situations and predominantly genetics play a huge role. In the Scott and Fuller study it was found that some dogs are genetically more prone to be reactive including the Beagle, Basenji, and the Wire-haired fox terrier to the Cocker spaniel and Shetland sheepdog.

If dogs have a bad experience with other dogs especially during the first 18 weeks of puppy hood it can have a great impact on their adulthood. They have learned that barking, lunging and growling at other dogs or even people keeps them at bay which then serves a purpose to the dog.

Attending puppy classes is a start to socialize your puppy but by far not enough exposure to different dogs, people and new environments.
Some dogs are just the opposite, they love other dogs so much that they get frustrated for not being able to get to the other dog to be able to greet and play.  This type of dog needs to learn impulse control.
Reactivity relates to a dogs' response to sudden changes in stimuli, such as a doorbell ring. The trigger is not always just another dog but can be many stimuli, including someone riding a bike, a bird flying over, a sudden noise, new people and many more. Our job as dog trainers is to help teach the dog to cope with a certain level of stress even when pushed over threshold and for owners to know how to manage such a dog in an ever changing environment.
It is not easy to live with an reactive dog. Some dogs are only reactive when on lead and others are reactive in any new situation or change in their environment even just if someone comes over to your house.

Do not set up expectations for your dog realise that he might never be social but that it is definitely worth working on it even if it means he is just tolerant of other dogs and or people. Every dog and situation is different but in my professional experience reactive dogs sometimes do not become social butterflies but they can learn to tolerate other dogs and different stimuli. Off course there is the exception where with patience, positive training and positive social sessions with other dogs can help a dog become open to playing with other dogs and more accepting of changes in its environment. We can definitely improve their quality of life and minimize their initial flight or fight response to new stimuli. This is also where I find Self-selection and communication plays a huge role in changing how they respond.
There are also alternative methods that can and even should be added to training and management including making use of essential oils, touch wraps and exercise where the dog needs to use his mind including nose work, agility, sledding to name a few.
My Beagle Joey will spot a dog in the distance and as the dog approaches he turns his head to look at me.  As he looks towards me he will catch me smiling, telling him what a good boy he is.  He turns again to look at the dog as he walks past and then back at me.  I praise his courage and the decision he made to remain calm in a situation that previously caused him fear.  As I often do, I go to shelters and work with the dogs to teach them calming behaviors making their chances of adoption greater. One afternoon like any other I noticed this very playful young Beagle running around in a pen with a few other dogs not knowing why someone would not want this vibrant dog.

When Joey first came into my life three years ago, he was extremely reactive, he would lunge towards other dogs that walked past or came close to him.  Before I adopted Joey he has learned to protect himself by guarding resources he valued. Not only would he lunge and bark at dogs when he was on lead but he would also recourse guard any object which meant he would bite if the person and or dog came close enough.

He had likely learned to protect himself by behaving in a threatening manner.   He has learned that each time he became "aggressive" he kept the "thread" at bay.

By re-directing his behaviour I was able to teach him coping skills so that he would be neutral when the before thread is approaching him.  By making use of positive reinforcement giving him choices he was able to feel safe and learning new wanted ways to cope with what previously pushed him over threshold. Reinforcing him for making good choices is what changed his behaviour for the better.

A default behavior gives the dog an alternative and makes him more positive and confident in a situation that previously made him insecure.  
The dog is then gradually exposed to increasingly stressful situations and is watched to see what alternative behavior he offers.  If the behavior is something that counters a previously undesirable behavior, the dog is rewarded.

If he chooses negative behavior, he is quietly removed from the situation until he is in a place where he can learn again.
The only way Joey knew how to deal with situations that he would feel frightened in was to growl, bark, lunge and even bite.  Suppressing that behavior with punishment would have probably worked momentarily, but as in most cases, punitive suppression does not change the way a dog feels, but merely treats the symptom not the cause which is likely to resurface again in a similar situation.  
Not only that, it is simply wrong to punish a dog for being nervous or insecure and only serves to make the insecurity worse.  Instead we can teach them what is acceptable behavior and at the same time the dog can feel confidant and better.