I have done my fair share of reading about this subject and belly, leg, and ear rashes, along with paw chewing are common symptoms of allergies, possibly from food. My dog gets really bad rashes in her ears and tries to scratch her back, but she is allergic to tons of stuff (grass, beef, fish meal, soy, flax, and weeds to name a few). The most common food allergies in dogs are wheat and corn (Nutro lamb and rice will work for these types of allergies).
Our vet said to give her dog a whole Benedryl (she is 55 lbs), but we only give her 1/2 of one when she is having an outbreak because I read it isn't good on their kidneys. We also changed her food to Authority with chicken, and bathe her at home once every 2-3 weeks to reduce itchiness. It has helped significantly!
If you talk to your vet, you can have an allergy test done and it will tell you almost everything your dog is allergic to. It will atleast give you an idea of what you should keep her away from. There are also special pet dermatoligists that may be able to help (they give the dogs specially formulated allergy shots).
Hopefully that helps and good luck!
My friends have 2 American Eskimos that were getting those same problem spots with rashes all the time and they would scratch till they were bald in those areas. First they were told they were allergic to the grass, so they took them out to do their business in the driveway and didnt let them run around in the yard, but they still were doing the same 6 months later even though there was no longer any grass in the yard, but lots of snow. The next thing they tried was Frontline Plus and at first it seemed it was helping some, but then they started back and upon talking to someone who was into proper nutrition for dogs told them to stop buying dog food that has corn in it. Plus they had to stop giving them left over corn as well. In about a month we could all notice hair growth where there was no hair at all. They kept up with this plan and still use it and the dogs have almost grown all of their hair back. I am not a professional by no means, I just knew that your dog seemed to be having the same symptoms as theirs did. You might give it a try, it will take some doing to find dog food that has no corn or corn by products in it. I dont remember what the name of the dog food is but they did find it at Walmart. What have you got to lose to just give it a chance for a few months to see if it helps or not.