hot spots

I have a 4 year old dobermann, she is perfectly normal in health and has a wonderful silky skin, the only problem she is facing is having hot spots on her back. I have uploaded few pictures of the hot spots. The vets are treating her for flea, but it has not reduced. Please advice me as to what this symptom shows and possible treatment. She is also trying to mutilate the hot spots whenever it itches.
   
Dogs food habit - Egg with rice home made, milk and 4 egg white.
   
She is very active and alert.