In recent years, especially post-pandemic, dog trainers have seen a huge rise in dog reactivity cases. But what exactly is reactivity, and what signs should you look out for as an owner that might indicate you have a reactive dog?

Dog reactivity is a complex but common behaviour challenge. My experience has been that it exists on a spectrum with varying triggers - and it can’t always be defined as being caused purely by nature or nurture.

Some dogs may be genetically predisposed to anxiety or even aggression. Others develop reactive behaviours due to experiences in their early life or after traumatic incidents as an older dog.

Reactivity can range from frustration-based behaviours (such as a dog pulling and barking because they can’t greet another dog) to fear-based or aggressive responses.

Over 50% of owners of reactive dogs report avoiding social situations because of their dog’s behaviour.

What is Dog Reactivity?

Dog reactivity is a spectrum, not a single behaviour. A reactive dog may be displaying behaviour because of:

Frustration - e.g., wanting to greet another dog but being held back
Fear - feeling threatened by something in the environment
Aggression - an intent to make something go away

Some dogs are genetically predisposed to anxiety or over-arousal. For others, early life experiences or traumatic incidents - even as an adult - can trigger dog reactivity.

Why Early Socialisation Matters in Preventing Dog Reactivity

A study in Applied Animal Behaviour Science highlighted that dogs who had positive, structured socialisation experiences during their critical development period (roughly 3-14 weeks of age) showed fewer fear-based behaviours and were more adaptable as adults. For owners of reactive dogs, this underscores the importance of safe, controlled exposure in puppyhood - and for those with adult dogs, it reinforces why we must take a slow, intentional approach to reintroducing them to triggers to avoid creating more fear or frustration.

Dogs socialised positively between 3-14 weeks are less likely to develop fear-based reactivity.

Common Triggers for Dog Reactivity

Most reactive dogs have specific triggers, which can include:

Other dogs
Humans, particularly strangers or people wearing unusual clothing (e.g. high-vis jackets, helmets, hats)
Vehicles - cars, bicycles, scooters
Loud noises - fireworks, banging doors, or construction work
Other animals - livestock, squirrels, cats, birds
Fast movement - running children, joggers, or cyclists

What Does Reactive Behaviour Look Like?

A reactive dog may display one or more of the following behaviours:

Lunging towards the trigger
Barking, growling, or snarling
Whining or crying
Staring or “fixating” on the trigger
Avoidance - trying to hide or run away
Redirected aggression - nipping or biting the handler or another dog when frustrated on a lead
Changes in body language - raised hackles, stiffened posture, tucked tail, or frantic high tail wagging

72% of reactive dogs show stress signals before barking or lunging.

How to Help Your Reactive Dog

If you’ve noticed signs of dog reactivity, it’s important to act early. Reactivity, no matter the trigger, can be stressful and isolating for owners. Research published in the Journal of Veterinary Behaviour found that stress in dogs manifests both physiologically (elevated cortisol levels, increased heart rate) and behaviourally (barking, lunging, avoidance). For reactive dogs, this means the behaviours we see are often just the tip of the iceberg - their bodies are also experiencing a heightened stress response. This is why repeatedly exposing a reactive dog to its trigger without the right support can worsen the problem - it can reinforce the stress pathway in the brain, rather than desensitise it.

Here are key steps to help:

Work with an experienced dog trainer - Look for a trainer with experience in working with dog reactivity. They should create a tailored plan and guide you through management strategies while training takes place.
Avoid “quick fix” promises - Reactivity is not something that can be solved overnight. Be wary of trainers offering guaranteed results in unrealistic timeframes.
Manage environments - In the early stages, avoid situations where your dog is likely to go “over threshold.” This might mean changing walking routes or times.
Learn your dog’s thresholds - Your trainer should help you understand when it’s safe to work through a scenario and when to step back.
Focus on mindset change - The goal isn’t just to stop the outward behaviour; it’s to help your dog feel calmer and more in control in those situations.

Another Journal of Veterinary Behaviour study compared training methods in shelter dogs and found that reward-based, choice-driven training significantly reduced stress signals compared to compulsion-based methods. While this research was in a shelter context, the principles apply to reactive dogs in home environments - giving the dog agency and rewarding desired responses helps build trust and reduce reactivity over time.

Repeated uncontrolled exposure to triggers can make reactivity worse, not better.

How to Stop Your Dog Reacting - in the Long Term

Stopping reactivity isn’t just about teaching “obedience” - it’s about:

Building engagement with you so your dog focuses on you instead of the trigger.
Practising loose lead walking to prevent frustration from lead tension.
Introducing gradual, controlled exposure to triggers in a way your dog can handle.

With time, patience, and consistency, most dogs can make huge progress. Many owners in Essex and Hertfordshire are surprised how much calmer and happier their dogs become when the focus is on understanding, training, and managing reactivity the right way.

Recommended reading:

Dog Reactivity - How to Help Your Reactive Dog