My BC is 7 months old, a spayed female named Sweets. (Sometimes she's Sweets and sometimes she's Monster.) I am a new member here but have been reading the board for about a month. This has been a great help for dealing with noise sensitivity - my dog would jump at my arm and bite (sometimes tearing cloth) when I sneezed loudly, or sharpened a knife - unusual noises. After reading posts here, I've been working with her to desensitize with click and treat.
We are also working to desensitize for brushing. She was okay as a very young puppy (there wasn't much fur to brush, though) but it was like overnight (at about 5 months) she got very upset with the brush, or toweling her off.
However, I'm a baffled about her behaviour in several cases: if she tries to get into the cats' food (which I've sometimes forgotten to remove before she comes in the kitchen where they eat), she gets very aggressive with trying to bite my arm and growling. She also had her nose in a box of kindling today, and when I told her "No - out of there", she went after me in the same way. I've found that raising my voice with a louder "No" just makes her worse. She will stop after a few lunges at my arm, then I make her sit, stay for a minute and ignore her for half an hour. I can (and do) take away her food dish when she's eating with no problem. It seems to be things she shouldn't be doing that bring out the bad behaviour.
She did get very aggressive when my husband (after taking her collar off to add a short piece of pink line, to make it easier to find the loop for the leash hook) tried to put her collar back on. He started yelling No and Bad Dog at her, which really made things worse. I think she didn't like being approached from the front, maybe the pink line scared her too; in any event, it took a while to calm her down and I was able to get the collar back on by taking her to the door, showing her the ball and attaching the collar from behind her.
She went through puppy class and basic obedience, gets on very well with other dogs and people. She gets lots of exercise, playing ball, chasing sticks and long walks in the woods; she also plays almost daily with two labs next door (one her age, one older).
My concern is that this behaviour may escalate, or broaden if I don't deal with it now. The noise desensitization has been quite encouraging, but I'm not sure I'm dealing with the same sort of problem in the other cases.