Skin Allergies?

I have a 9 year old female cocker spaniel who has had skin allergies pretty much her whole life. A while back she started chewing at the hind leg and between her paws. She'd chew so bad it would break open the skin and bleed. We recently got her shaved down because she was getting mats in her hair.

She still chews occasionally but not as severe as she was... now we are finding this little white spots that look like big dandruff that is matted to her skin.

Anyone that could help me out I would be more than thankful. We've been to the vet and were told to give her Benadril (spell) We also use hypo-allergenic shampoo on her.