DEB, What brand of food are you feeding? I believe this is food related like an allergy. Something causes an irritation to the skin and the dog chews and licks the skin and makes the problem worse. Shaving the areas and treating daily with Hydrogen Pryoxide with help to dry up the sores.
Some ingredients in dog food can add to the Hot Spot problem like Wheat, Corn, by-products, artificial anything, colors, preservitives, glutens etc. I haven't had any hot spots in my dogs for years since I stopped feeding foods with these ingredients. My food of choice for the last 5 years or so is CANIDAE. When you look at Canidae's ingredients you can see the difference. http://www.canidae.com
I have also found several food supplements that add healthy ingredients to the diet that can not be added to dry food due to the cooking process.
Here a some products to check out. There here are many more than these, you only need to use one, not all of them. I am sure any of these would help prevent hot spots from occuring again.
Norwegian Kelp Vegetarian Blend at http://www.kelpproductsofflorida.com
NUPRO Dog Supplement at http://www.nuprosupplements.com
"IN" Diet Supplement at http://www.alc-Inovators.com
Hope that helps