Why has my dog suddenly gotten aggresive?

I love boxers. Great big slobber hounds, ton's of energy and totaly dedicated to their family.

FIrst, check with a vet asap. Second, blow off the fair until you've cleared the vet. If the vet clears her then contact a canine BEHAVIORIST, not a trainer; well, to be fair one can generally do both rather well but it's dog behavior we want to understand here not teach her how to fetch and sit.

As to the random growl. Dogs sniffer's are quite delicate instruments and mean people stink. No, I'm serious, mean people give off an odor a dog can pick up so I wouldn't lose to much sleep about it.

I would take her the vet to rule out anything medical for starters. Then I would consult with a professional. When is the fair? I would find a behaviorist/trainer here:

http://www.apdt.com/

Do an inhome consultation. They will tailor a training plan for your dog. With a certified professional trainer/behavorist, they will evaluate the dog, come up with the training plan, then be available to you over the phone for future consultation at no additional charge to you. It can be an invaluable service. Be sure you don't go with a fear based training method, though, as this will only makes things worse over the long haul and can actually be a dangerous situation.

The dog aggression increasing can easily be explained because she is now hitting full maturity. What was once minor aggression will blow up into full blow dog intolerance. This is why it's good to bring in a professional now. Since dog aggression is a completely separate issue from human aggression, it shouldn't make your dog aggressive towards humans. Again, for this reason, I would bring a professional in to see what is going on.

Top of my list would be brain tumour. Secondly perhaps, even if you didn't know it, arthritis could have been setting in - and being around a boisterous younger dog would make her want to defend herself. Occasionally losing faculties, hearing/sight could cause her to fight first, and think about it second. The only way you might have known, would have been had you had your vet do a check, after she was put down. But you know it's all water under the bridge - and there's no point whatsoever putting yourself through the 'what-ifs'. I'm sure you did what was necessary at the time, with the information you had available at that time. Sad as it is, let go, focus on your current dog, and know she is at peace now.

You need to understand the breed, which you must do, if you're showing her. So think back to when it started and what could have triggered it.

But if she's 2 now, it sounds like she's now fully adult and exercising her rights. She should have been trained out of that aggressivity from the time she was a puppy. You may have to get a dog behaviour specialist to work with her if it continues.

Think twice about the fair. You should keep her away from all children until you have resolved the aggression issue.

Do you really want to be responsible for some child getting bit or mauled.?? You could loose your home.

i would bring her to dog parks when there arnt a lot of dogs there and dont let her off the leash whenever a dog comes by her and she doesnt growl give her a treat, and try to get her in an obedience class, so she will be around dogs and do the same thing, and if you have any friends have them bring there kids over and let one at a time pet her, and give her treats for being good, then go to the park with little kids and let the kids pet her one at time then 2 at a time so on... good luck