Hi
I had a maltese poodle who was allergic to everything. Couldn't bath her in anything except the Avolene (sorry can't think how to spell it) she would also get the itches from pet mince. If it was human grade mince she was fine but pet grade would cause problems.
I now have a pit bull staff cross who is starting to get "hotspots" which I am sure is caused though the grass. Not much I can do with that just yet, except keep her inside as much as possible.
I wish you luck in your endevour to stop Minx's itches. I agree though I wouldn't use tea tree oil on my dogs. I will have a look I do have a home made shampoo recipe for stop itch shampoo and it makes up enough to bath both my dogs and all 4 of my cats once.
Mumtosix