Imovex is very strong stuff, but it is very commonly used for all sorts of animals. Aside from dogs, I've seen it used on guineas, horses, and even mice. We had to use it on our pet mice for mites, and it really helped them. However, lots of things can cause skin issues. It's always good to see a vet first, and to go from there. If it's mange or a mite problem, you can at least narrow it out right away. If it's not, it can be anything from Staph or chaffing from exercise (as the other posters have mentioned) to thyroid conditions (can cause hair loss or rashes) to topical or food allergies (my dogs had horrible skin problems from those).
Skin stuff is always kind of a mystery that way. As the owner of two dogs who suffered greatly from rashes and baldness over a year before we figured out they were allergic to fish in their dog food, I wish you luck into getting to the bottom of it quickly.
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