Why Is My Dog Being Aggressive All Of A Sudden? – Find Out Here

May 16, 2021

our dog decided that she’d had enough. The aggression you’ve been seeing from her lately is something that’s been coming on for a while. You just didn’t recognize it, because it started small and got progressively worse. You may have even given in to her demands and allowed her to get away with certain behaviors that you wouldn’t have approved of before. (Most people do.) But now, you’re faced with the ugly truth: your dog is being aggressive all of a sudden.  It’s only a matter of time before someone gets hurt.

Dogs Showing Aggression

Knowing why your dog is acting aggressively is essential to figuring out the best plan for stopping this frightening behavior. There are several potential causes of aggression in dogs.


Fear and Anxiety

  • Fear
    • Specific and targeted.
    • Dogs might be afraid of dogs, bicycles, children, a specific child, men with hats, etc.
  • Anxiety
    • Generalized and vague.
    • Dogs may feel anxious about not knowing what is going to happen or how another might react. They may feel on edge or be too worried to fully let down their guard.
  • Fear/Anxiety about negative feelings
    • Not usually discussed in regards to dogs but should be addressed. The feeling of fear and anxiety is very negative. Dogs may act out to avoid feeling anxious or fearful. For example, in the case of dogs who are worried about responses from others, may test them to get much-needed information. They may also act out of jealousy


It is well known that pain can elicit aggression in dogs, Pain is often a normal response to pain, however, a learned component can develop.

If dogs experience pain in certain situations, they may develop a habit of responding aggressively even when the pain is no longer an issue.

Dogs frequently do not show pain and we may be unaware of how they are feeling until something becomes so obvious we can’t miss it. Whenever a dog becomes aggressive, medical issues should be explored.

  • Physical pain
  • Dental problems, arthritis, sore paws, backs, joints, sore paws, digestion problems, etc. Check out the medical causes of dog aggression for more information.
  • Poor health
    • Fatigue, lethargy, depression, etc.
  • Negative feelings.
    • irritation, jealousy


Frustration is an unmet need or desire and can contribute to aggression in dogs. In all likelihood, there are varying degrees of frustration, and at some point, there may be a tipping point. Some scenarios that may cause frustration in dogs.

  • Feeling trapped
  • Needs not being met adequately
  • Being forced or coerced into doing something again there will
  • Not having sufficient control over one’s environment
  • Personal space may not be respected
  • Confusion about expectations and or punishments
  • Being blocked from accessing a desirable thing
  • Redirected aggression, Leash aggression, Boundary or Fence aggression can all be an example of aggression that may be frustration driven

Signs of Aggression in Dogs

How can you tell if a dog is nervous to the point of being aggressive? What kind of body language and signs is a precursor to an attack? Knowing the answer to these questions can help you anticipate aggressive behavior, and, hopefully, stop it in time.

Apart from Sudden Onset Aggression syndrome, which is a rare condition, an aggressive attack can always be predicted by the specific behavior that precedes it.

Here are the most common signs of aggression in dogs:

  • Stiff body posture
  • Ears pinned back
  • Growling
  • Baring Teeth
  • Snarling
  • Bites of different intensity (from light snipping to puncturing bites)


1. Fear

Fear is the most common reason for dogs to behave aggressively toward other dogs. Fear-based behavior often occurs through a lack of proper socialization, past negative experiences with other dogs, or abuse at the hands of previous owners. Usually, a dog will only exhibit aggressive fear-based behavior if they feel in danger and need to defend themselves.

2.Resource Guarding

Dogs exhibiting resource guarding are aggressively possessive of the things they most cherish – like their favorite toy, treat, or even human. Dogs that are resource aggressive may lunge and at times snap at other dogs for getting too close to their bed, favorite chew toy, or dog mom/dad. If your dog shows these signs, please consult your vet as left unchecked, resource aggression can escalate to severe physical attacks


Recent changes in a dog’s environment might be making them anxious, causing them to exhibit aggressive behaviors. Anxiety might be caused by the arrival of a new family member or moving to a new home.

4.Social Aggression

When multiple dogs coexist, they will work to establish a hierarchy for the pack. This rank and file system allows the pack to establish an order to things like who gets the coziest napping spot or is the first to eat. However, in times where a lower pack member disturbs the order, the Alpha dog might correct them with a display of aggression in the form of a growl or snap.

5.Leash Aggression

Is your dog is friendly and approachable most of the time? Does your dog start barking, lunging, or snapping at everything in sight as soon as you put on their leash? If so, your dog is leash-aggressive. Leash aggression is usually directed at other dogs and is known to stem from your dog feeling too restrained by their leash.


We aren’t talking about the desirable protective behaviors we all hope our dogs display for our families and homes. Instead, the very dangerous behaviors result when dogs become hyper-vigilant over their perceived territory.7.Frustration

Often called redirected aggression, this is frustration that stems from a dog not being able to get to something. The dog then takes out their frustration in other ways – usually at the expense of another pet or even a human.


Some illnesses cause dogs to become aggressive. If your dog loves to horse around with their furry friends, but recently has become quick-tempered and lashes out, they may be suffering from a serious medical ailment.

Factors that contribute to Dogs aggression

Physical Aspects

From how we’re wired to the coping mechanisms we use, there are many things about aggression that go beyond what has happened before and what is happening at the moment.Here are just some of the things about dogs as physical beings that can influence aggression.

  • Temperament
    • Reactivity can contribute to dog aggression
    • Coping styles and tendencies
  • Genetic
  • Congenital (present from birth) diseases, disorders, or conditions
  • Hormonal (levels and receptor density)
  • Neurophysiologic
    • The science relating to physiology and how the brain works in conjunction with the nervous system


Past learning affects how dogs respond to occurrences in the present.Fear, negative experiences, failures, and successes greatly shape how a dog responds now.

  • Negative experiences
  • Associations linked to negative experiences
  • Generalizing experiences from negative experiences
  • Poor socialization


There is a critical period in a puppy’s development where they need to be exposed to a variety of different things they might encounter in life.

Otherwise, they can often develop a fear of those things later on. Some dogs need to be continually exposed to a variety of things in a positive way to maintain this confidence.

Dogs with poor socialization histories during the critical phase or who have learned fear from a negative experience are not beyond help. Behavior modification may take longer but it’s possible to make life better for these dogs (and for you!)


We primarily focus on the immediate circumstances of aggression as a way of understanding it.But stress can play a big factor in the development of aggression and we might not even be aware of what is contributing to it, or how we can alleviate it. In some cases basic – and simple – changes can make a big difference. Here are some factors that could be playing a role:

  • What occurs immediately before the aggression
  • Social interaction and mental stimulation
  • Stress in the environment (ie. noise, threats, frustrations)
  • Predictability (ie. routines and schedules)
  • Exercise needs
  • Nutrition needs and affects
  • Boredom

What we do to make dog aggression worse

Our intentions are usually good but there is a lot of things we can and often do that make things worse.

Allowing the aggression to continue to occur

Dogs are not simply misbehaving. Aggression is not just “behavior”, it is a coping response.

But each time the aggression occurs, the brain rewires itself to be a little better at making that process occur more efficiently and effectively.

Using Some training methods

In many cases, aggression can attract the kind of responses from humans that make the situation worse.

 Either we become frustrated or we take on bad advice such as intimidating the dog as a way to try to deal with it.

Unfortunately outdated methods that have been popularized by the media can make dogs who are predisposed to aggression worse (Dogs don’t choose to be fearful or anxious or frustrated.)

Ignoring the Dog signs of stress

We miss the signs that we could act on to help our dog avoid unnecessary stress. Behaviors such as turning the dog turning his or her head away, stiffening, licking the lips, putting the ears back are just a few.

These signals are important to learn if we have a reactive, fearful or aggressive dog.

Not meeting needs

These days most of us have a lot going on. Sometimes we don’t always meet the needs of dogs.  Dogs need stimulation, exercise, social experiences, proper diet, a certain amount of freedom in many conditions, routines.

 A dog that is left alone for long periods of time, is left outside all day on the end a leash, is ignored, is bored, frustrated, etc. is going to have more problems than one whose needs are met.

Health concerns

Sudden aggression in dogs might be a result of medical issues that contribute to dog aggression or simple pain or discomfort of any sort.   It is very common for dogs that are seen by a veterinary behaviorist to also have medical conditions as well.

Your first step should be to see a vet.  However, even when the dog’s aggression is completely a result of pain, you will likely need to do behavior modification to change the associations your dog developed while the situation developed.

Assuming that “That’s just the way the dog is”

You should talk to your vet about any unusual behavior, whether it’s repeated paw licking, excessive drinking, barking at nothing, chasing imaginary flies, lying with a head under a seat, etc. In particular, anxiety may manifest in unexpected ways and this may shed some light on your dg’s aggression issues.

Steps for treating your Dog aggressiveness


Avoiding aggression is essential in treating the underlying cause. Don’t get caught up in the trap of thinking that punishment will “change” the behavior. Aggression is at the tail end of the behavior sequence – not at the beginning. Each time the behavior sequence occurs, the brain rewires and it becomes more likely to be repeated, regardless of punishment.

  • Get further distance from the circumstances and situation that cause the anxiety and aggression – You might be interested in 6 Other ways to keep others away from your dog
  • Teach your dog a variety of commands and cues that can help you navigate a situation where you can’t get enough distance right away and your dog might start feeling anxious
  • Avoid the circumstances and situations that cause anxiety and aggression – see how anxiety is related to aggression. For example, if the dog reacts when pushed off the bed, stop pushing them off the bed for now

Meet Needs

Dogs have a variety of needs – from basic needs for exercise and social interaction to more complex needs for medication. Some needs are general to all dogs, and some very specific to the individual. Anxious dogs in particular are more vulnerable to stress. Therefore several stress-reducing strategies should be included to meet the needs of the dog. At a minimum:

  • Consult your veterinarian to rule out any medical causes of aggression.
  • Develop a safe and trusting relationship and environment
  • Ensure your dog’s basic needs are being met adequately. Going above and beyond may actually improve stress and passively improve aggression.

Behavior Modification

Behavior modification can be done both passively and actively. You can change behavior indirectly and/or target behavior modification to a particular situation. Either way, the goal is to change behavior by targeting the underlying cause. This means strategies to reduce anxiety, develop better tolerance and better-coping skills and create new positive associations:

  • Teach your dog how to relax
  • Develop your dog’s ability to self-control
  • Treat the underlying causes

Can We Cure Aggression?

Pet parents of aggressive dogs often ask whether they can ever be sure that their dog is “cured.” Taking into account the behavior modification techniques that affect aggression, our current understanding is that the incidence and frequency of some types of aggression can be reduced and sometimes eliminated.

However, there’s no guarantee that an aggressive dog can be completely cured. In many cases, the only solution is to manage the problem by limiting a dog’s exposure to the situations, people, or things that trigger her aggression.

There’s always a risk when dealing with an aggressive dog. Pet parents are responsible for their dogs’ behavior and must take precautions to ensure that no one’s harmed. Even if a dog has been well behaved for years, it’s not possible to predict when all the necessary circumstances might come together to create “the perfect storm” that triggers her aggression.

Dogs who have a history of resorting to aggression as a way of dealing with stressful situations can fall back on that strategy. Pet parents of aggressive dogs should be prudent and always assume that their dog is NOT cured so that they never let down their guard.

Breeds More Aggressive Than Others

Some breeds might indeed be more likely to bite if we look at statistics gathered on biting and aggression. There are many reasons for this. One likely reason is that most dog breeds once served specific functions for humans.

Some were highly prized for their guarding and protective tendencies, others for their hunting prowess, others for their fighting skills, and others for their “gameness” and tenacity.

Even though pet dogs of these breeds rarely fulfill their original purposes these days, individuals still carry their ancestors’ DNA in their genes, which means that members of a particular breed might be predisposed to certain types of aggression.

Despite this, it’s neither accurate nor wise to judge a dog by her breed. Far better predictors of aggressive behavior problems are a dog’s individual temperament and her history of interacting with people and other animals.

You should always research breeds to be sure that the breed or breed mix you’re interested in is a good fit for you and your lifestyle. However, the best insurance policies against aggression problems are to select the best individual dog for you.

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Hey yaa! Im Ashly and I love pets. Growing up in a house with 2 dogs, a cat, a parrot and many furry rodents; it was natural for me to have a profound affection for them. I created GenerallyPets.com to create useful guides and articles on looking after your furry friends. The advice given on this site is our views and expertise, please consult a VET prior to testing anything. Hope my site helps you :)

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