Reactivity is a common term in dog behaviour circles, but it is often misunderstood. At its core, reactivity describes a dog’s heightened and often disproportionate response to a stimulus. This might be another dog, a person, a vehicle, or even a sound. A reactive dog typically overreacts in a way that appears sudden, loud, or aggressive, but the truth is usually much deeper and rooted in fear.
Fear as the Underlying Cause
In the vast majority of cases, reactivity stems from fear. Dogs, like people, have a range of natural responses when they feel threatened. These are commonly described as fight, flight, freeze, or fidget. A reactive dog might bark and lunge, try to run away, become motionless, or show displaced behaviours such as sniffing the ground or scratching. Although the outward signs might vary, the internal emotion is often the same, fear.
What Reactivity Looks Like
Reactivity does not look the same in every dog. For some, it involves barking, growling, or lunging at triggers. For others, it could be whining, hiding, or becoming hyper-alert. Some dogs redirect their frustration by spinning, grabbing the lead, or nipping the nearest person or dog. It is important to recognise that none of these behaviours are bad in a moral sense, they are coping mechanisms in response to stress.
When Communication is Ignored
Dogs communicate discomfort long before they growl, snap, or bite. They might turn their head away, lick their lips, yawn, freeze, or try to create distance. These early signs of stress or unease are often subtle and easily missed or dismissed. If a dog learns that these signals do not work, they may stop using them altogether and escalate straight to more forceful behaviours. This is sometimes described as a dog getting in there first, biting before something scary happens in order to protect themselves. It is not about dominance or bad temperament, it is a survival strategy that develops when quieter warnings have been repeatedly ignored. Recognising and respecting a dog’s early communication is essential. It allows us to intervene, support them, and prevent situations from reaching crisis point.
The Importance of Early Socialisation
One of the best ways to prevent reactivity is through careful, positive early socialisation. This does not mean simply exposing puppies to lots of experiences, but making sure those experiences are enjoyable, safe, and at the puppy’s pace. A well-socialised puppy is more likely to develop into a confident adult who feels safe in a variety of environments. However, it is important to remember how fragile this window of development can be. Just one frightening experience during a puppy’s socialisation period can set them back significantly, especially if they are already nervous or sensitive by nature. In some cases, a single negative interaction, such as being attacked by another dog or handled roughly by a stranger, can shape how that puppy sees the world going forward. For adult dogs, repeated stress or one severe incident can have the same effect. A dog who was previously coping well may become wary, defensive, or reactive after a traumatic experience. Trauma, whether it happens in one moment or builds up over time, can leave deep emotional scars. This is why creating positive, well-managed experiences is just as important for adult dogs as it is for puppies.
A Hidden Crisis, Behavioural Euthanasia
Many people worry about deadly diseases such as leptospirosis or parvovirus, and rightly so. These are serious illnesses that can pose real risks to young puppies. However, in trying to protect their puppy’s physical health, some owners delay or avoid socialisation altogether during the critical early window. Sadly, this well-intentioned caution can have lasting behavioural consequences. The socialisation period, typically between three and sixteen weeks of age, is a vital time for puppies to safely learn about the world. If they miss out on positive, controlled experiences with people, dogs, places, sounds, and handling during this phase, they may grow up fearful and reactive. In some cases, a lack of early socialisation leads to serious behavioural challenges that make it difficult for dogs to live comfortably in everyday life. The tragic irony is that while parvovirus and leptospirosis are rare in well-vaccinated areas and can often be prevented, behavioural problems stemming from lack of socialisation are common and can be harder to treat. In fact, more dogs are euthanised due to behavioural issues, particularly fear-based aggression, than from either of these diseases1. By balancing cautious exposure with appropriate hygiene and avoiding high-risk environments, it is usually possible to socialise puppies safely and effectively. Education and support are essential, not just in preventing illness, but in building resilient, confident dogs who are more likely to thrive in our busy world.
Other Causes of Reactivity
While fear is the most common root, reactivity can also stem from frustration, pain, poor impulse control, or a lack of appropriate outlets for energy. A dog who barks and lunges at the end of the lead may not be aggressive, but simply frustrated at being unable to reach the object of interest. Dogs in pain or discomfort may also have a lower tolerance for stimulation and react more strongly to perceived threats.
Thresholds and Individual Differences
Every dog has their own threshold, the point at which they become reactive. This varies greatly between individuals and can change depending on context, health, fatigue, and previous experiences. For example, a dog who copes well with passing joggers in the park may find it overwhelming on a narrow footpath. Understanding and respecting a dog’s threshold is key to helping them feel safe.
Trigger Stacking and Cortisol
When dogs experience multiple stressors in a short period, they may become overwhelmed. This is known as trigger stacking. A dog might cope with one trigger, like a noisy bin lorry, but then struggle to cope with a second, such as an off-lead dog rushing up. Each event increases the level of cortisol, a stress hormone, in the dog’s body. Cortisol can take several days to return to normal, and during that time the dog may be more reactive or sensitive than usual.
Reading the Environment and Setting Dogs Up for Success
One of the most important skills a guardian can develop is the ability to read situations when out walking their dog. This includes reading your own dog’s body language, understanding breed-specific traits, and observing the behaviour of other dogs and people nearby. It allows you to make informed decisions that protect your dog’s confidence and wellbeing. For example, many Whippets enjoy a game of chase, especially in open spaces. However, their light build and gentle nature mean they can quickly become overwhelmed or even bullied if play becomes too rough or unbalanced. Some dogs, particularly more physical or excitable breeds, may not understand when a Whippet is uncomfortable or trying to disengage. This is where close observation and early intervention are essential. Setting your dog up for success means choosing appropriate walking environments, avoiding high-risk situations, and staying alert. If you see an off-lead or out-of-control dog approaching, remain calm and assertive. Step calmly to the side or create distance, and use your voice in a clear and confident tone to ask the other dog’s owner to call their dog back. If there is no owner in sight, create space as quickly and safely as possible. Avoid picking your dog up, especially if they are anxious. This can increase their stress and draw attention, sometimes prompting a chase response from the approaching dog. Instead, position yourself between your dog and the oncoming dog if needed, and focus on remaining a calm and grounding presence. Moving away together while maintaining connection and composure is often the safest and most effective option.
The Role of Medication in Behavioural Support
In recent years, there has been a growing understanding of how certain medications can help support behaviour modification. Drugs such as fluoxetine, a selective serotonin reuptake inhibitor, can reduce anxiety and help a dog feel safer and more capable of learning. Medication is not a shortcut or a standalone solution, but it can be a valuable part of a broader plan that includes training, environmental management, and emotional support. For some dogs, it can be life-changing. It goes without saying that veterinary advice must be sought for this.
Counter-Conditioning, Changing the Emotional Response
One of the most effective ways to help a reactive dog is through counter-conditioning. This process involves changing the dog’s emotional response to a trigger. For example, if a dog feels scared when they see another dog, we can pair the sight of that dog with something they love, such as chicken or cheese. Over time, the dog starts to associate the presence of other dogs with good things happening, and the fearful response begins to fade. Counter-conditioning must be done carefully and gradually, keeping the dog below their threshold and always working at a distance where they feel safe. With consistency, many dogs show remarkable improvement.
Professional Support
A few sessions with a qualified and experienced behaviourist can go a long way to helping you identify the cause of reactivity and how to address it. They can often provide stooge dogs in suitable environments to enable you to practice counter-conditioning.
https://www.petprofessionalguild.com
In Summary
Reactivity is a fear-based behaviour that often reflects a dog’s internal struggle to feel safe in the world. It is not a character flaw or a sign of a bad dog. With early socialisation, attention to communication, breed-aware handling, patient behaviour modification, and, where needed, the support of medication, dogs can learn to feel more at ease. Supporting dogs through their fears not only improves their quality of life, it also strengthens the bond they share with us.
1 (PDF) Factors associated with behavioral euthanasia in pet dogs
After growing up with terriers and gundogs, I adopted my first retired Greyhound in 2013 who was quickly joined by another. In 2016, a rescue Saluki lurcher joined the family. In 2018 I decided I’d like to have my first puppy and a Whippet fitted the criteria. I ensured I got one from a responsible, ethical breeder. Rocket arrived in November 2018 and was followed by Atlas in 2021
Carly Soffe (Rockatom)