How to Solve Aggression in Dogs

There are several causes for hostility in dogs

causes of aggression in dogs
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It can be a frightening experience: A usually docile, friendly dog suddenly becomes aggressive, growling, lunging, or baring its teeth. In an extreme case, the dog may bite or attack you or a family member it knows well and has never acted against before.

It can be difficult to know what to do when your dog shows these signs of hostile behavior. Since dog aggression can get out of hand and result in injuries to dogs or people, it's very important to find the cause so you can help your dog overcome the aggression.

Why Do Dogs Show 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.

illustration of causes of aggression in dogs
Illustration: Katie Kerpel. © The Spruce, 2018

Illness and Injury

Some medical conditions can cause dogs to become aggressive. If a dog that has never shown any sign of aggression suddenly begins growling, snapping, or biting, it may be caused by a disease or illness.

Pain is an especially common cause of aggression in dogs. Your suddenly aggressive dog may have an injury or an illness that's causing major discomfort and stress. Some possible causes of pain include arthritis, bone fractures, internal injuries, various tumors, and lacerations.

Other illnesses may affect your dog's brain, leading to seemingly unreasonable aggression. Brain diseases or tumors and cognitive changes in older dogs are a few brain conditions that may provoke the onset of aggression.

If your dog is exhibiting sudden, unexplained aggression, talk to your veterinarian before attempting to address the behavior.

You may want to try giving your dog medication if you sense it's in pain or suffering. Don't do this. If your dog is sick, you'll need to know exactly what is wrong with it before you begin any treatment. Don't try to take matters into your own hands until you know what you're dealing with.


A fearful dog can become aggressive. Most dogs only exhibit aggressive behavior if they sense they're in danger, are unable to escape, and need to defend themselves. This can occur if a dog is backed into a corner with no way out or if it thinks the hand you raised over its head means you're going to hit.

If your dog is a rescue dog that exhibits aggressive or fearful behavior more than is normal, it may have been abused, neglected, experienced a traumatic event, or not properly socialized as a puppy. Any information you can get from the organization where you adopted the dog could help you determine the best way to handle the situation.

Sometimes rescue dogs need obedience training with an instructor who specializes in teaching dogs that have been abused, and other times, you may be able to manage your dog's fear with patient care. Do speak to a veterinarian about the best course of action.

To avoid provoking this type of aggressive behavior, approach unknown dogs carefully (better yet, let them approach you). Train and socialize your dog to help prevent fear down the road.


Possession aggression, or resource guarding, occurs when a dog is possessive of food, a toy, a bed, your yard, or some other object of value. A dog that exhibits possession aggression may growl if someone approaches its food bowl or gets close when it's chewing a favorite toy.

A dog may also bite a stranger who steps into your home, which is the dog's territory.

The degree of aggression may vary from one dog to another and between objects. For instance, your dog might not care if you sit down and pet it while it's chewing a rubber toy, but it may turn and snap at you when you do the same thing while it's chewing a pig's ear. It all depends on the value that the dog attributes to each object or resource.

Dog pulling toy from man's hand
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Aggression that's caused by frustration is often referred to as redirected aggression or barrier frustration. It occurs when a dog is frustrated at not being able to get to something and takes its frustration out in another way. This type of aggression is often seen in dogs that spend a lot of time tied up, restrained on a leash, or behind a chain-link fence.

For example, a dog that's chained in a yard may spend the day straining to get to a dog that lives across the street or in an adjacent yard. The restrained dog usually barks and growls more fiercely as the frustration grows. When the owner approaches, the dog may redirect its frustration and bite the owner.

Establishing Dominance

Dogs sometimes show aggression to establish dominance. This is more commonly directed toward other dogs, but it can occur with people as well.

Dogs that display this type of aggression feel that they must prove they're in charge of a situation. The growling, snapping, or biting occurs when they feel their position is being challenged. Unfortunately, people often mistake the cause of canine aggression as dominance-related behavior when there may be another cause.

Be careful not to misinterpret your dog's aggression. Always rule out a health issue or fear before you assume you know the reason for your dog's aggressive behavior. Otherwise, attempts at corrective measures could actually make the problem worse.

Two Dogs Fighting On Lawn
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If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.