Why has my dog recently started acting aggressive?

My English Mastiff recently started acting aggressive at times to our cat and my son. She has been drinking water excessively and has had a...

Dr. Eric Barchas  |  Apr 12th 2007


My English Mastiff recently started acting
aggressive at times to our cat and my son. She
has been drinking water excessively and has had a few
accidents in the house. I did make an appointment
with her vet but I would like to have your advice
first. Thanks.

Carrie
Location not specified

Animal aggression against people is an extremely serious matter. I recommend that the owner of a pet that acts aggressively towards any person, especially a child, take serious precautions. This recommendation applies to the owners of aggressive cats and Chihuahuas, but it is especially important if you own an animal, such as a Mastiff, that is large enough to cause serious injury.

First, in the short term, do not allow situations to arise in which your dog might be able to injure the cat or your son (or anyone). This may mean keeping them physically separated, or keeping the dog isolated.

Second, you have done the right thing by scheduling an appointment with your vet. Situations in which pets act aggressively always warrant professional help. Your vet may be able to identify the cause of the aggression, or help you to modify your pet’s behavior.

There are two general causes of aggression: medical problems and behavioral issues. Sometimes a combination of the two is involved.

You mentioned that your dog is drinking more water. This is a symptom of several medical conditions. Some hormonal irregularities, such as thyroid gland or reproductive organ problems, can cause aggression and increased thirst. As well, urinary tract infections can cause accidents in the house, and the associated pain can trigger aggression. Your veterinarian should be able to identify whether any medical problems are playing a role.

Aggression that is caused exclusively by behavioral issues can be very difficult to treat. Because of its serious nature, many people in your situation seek consultation with a specialist in veterinary behavior.

Even if you are able to control this situation, I strongly recommend that you be vigilant in the future to ensure that your dog does not have the chance to injure any person or animal.