Note: We do not currently have a health liaison for this disorder. If you would like to volunteer, please contact and we will be happy to answer any of your questions. For a description of the position, please click on disorder health information liaison or health information reviewer.


Thank you to Helen Newman for putting together this article for SCARF.

Aggression in dogs is a normal behavior when displayed in the correct context. “It is best defined within a given context as an appropriate or inappropriate threat or challenge that is ultimately resolved by combat or deference. Most aggressive dogs are clinically behaviorally abnormal, but the abnormality is usually progressive and is influenced by the social environment.” (Overall, 1997). When the behavior of the dog is causing problems between the dog and the owner, with other dogs, or other people you must realize there is a problem of aggression. Aggression can be divided into a multiple of categories, ranging from 8 to 13, and a dog may fit a multitude of the categories.

Signs and Symptoms

Remember to look at these in the context of the situation. And that there may be other subtle signs of reactivity.

Vocal: excessive uncontrolled barking (increased agitation), growling, snarls, lip lifting (usually this is silent), and/or snapping and biting.

Physical signals: posture of body –standing rigid, hair up, ears back, walking stiff legged, tail wagging and staring. Please note that a wagging tail only means a dog’s willingness to interact!

Guarding of territory, food, possessions, humans, etc.

Grabs people’s hands, clothing, legs with teeth


Abnormal aggressive traits may be a caused by a combination of genetics, environment, the breed and medical causes.

Medical causes

Brain chemistry


Encephalitis (bacterial or viral) Distemper


Hydrocephalus in brachycephalics


-–Brain tumors

Head trauma

Behavioral Seizures

Diagnostic Tests

Medical tests should be done to rule out a medical reason for the aggressive behavior. The dog, owner and any individuals that are daily involved with the dog should be evaluated by a trained animal behaviorist or clinician. How the dog and humans interact normally must be evaluated by a trained professional.

Other areas that should be evaluated to help with the diagnosis is age of onset of problem, how long has it been occurring, any changes in daily patterns, can you predict when the aggression will occur, and how does the dog respond to any modifications you the owner does.

Treatment Guidelines

Note: Treatment of animals should only be performed by a licensed veterinarian. Veterinarians should consult the current literature and current pharmacological formularies before initiating any treatment protocol.

Once the aggression has been accurately diagnosed, the client should avoid circumstances that provoke the aggression so the dog does not learn from the inappropriate behavior.

The clinician will design a behavior modification plan that fits the dog and the household.

This may include:

  • neutering/spaying
  • behavior modifications (dog and human): relaxation, gradual change, rewards, reinforce proper behavior
  • modifying the environment: crates, fencing, number of other animals in the household, incentives
  • Use of head collars, harnesses, appropriate toys, leashes when inside
  • Medications may be prescribed
  • Follow up assessment with the clinician to decide next step of modification


Any behavior or environmental modification that one does to get the situation manageable will be a LIFE LONG commitment. There will be times of set backs but following through and staying with the program designed for you and your dog is necessary.

If a set back occurs though, one should consider discussing with the clinician for advise and to reevaluate any changes that may have occurred in the household (a move, change in routine for dog and human, less time for the dog, etc.)

If the recommended program does seem to be working, one should follow up with the clinician to discuss the situation.

The dog and the owner must be reeducated and learn the appropriate response to situations. It takes time and committment for any modification program to work.


Overall, K.L., “Clinical Behavioral Medicine for Small Animals”, Mosby, Inc. 1997 four bones rating two bones rating

1 bone 2 bones 3 bones 4 bones (full description of ratings)

Support Groups

Canine aggression



Animal Health Channel two bones rating

K9 aggression two bones rating

Protein aggression two bones rating

Hill Top Animal Hospital -Dominance Part 1 two bones rating

Hill Top Animal Hospital - Dominance part 2 two bones rating

Hill Top Animal Hospital Aggression two bones rating

Tellington-touch TTOUCH for companion animals two bones rating

Canis Major two bones rating

1 bone 2 bones 3 bones 4 bones (full description of ratings)

Current Research

Managing Aggression