itchy cocker spaniel

Question
I have a cocker spaniel that is almost 2 and spayed.  She has had some skin funk from the time I got her.  She had brown greasy ares in her groin.  The vet did a skin scraping and saw nothing but treated her for mange just in case.  Well that has never cleared she has recurrent ear infection and now in the last two months has begun chewing her feet and legs and continues to lick at her groin area .  I have tried multiple foods so called hypoallergenic and suppliments... the vet even gave me a new shampoo that is allergen repellent but doesn;t seem to help.  Last visit I was told "cocker ears and skin'not much to do.. but she is getting worse.....benadryl only makes her sleepy dosen't help the skin issue ... any help would be appreciated,

Answer
You need a new vet.  And Benadryl is the very least effective antihistimine for dogs.

How often are you bathing her and with what?
What are you using to clean her ears and how often?
What are you feeding her?
Does her coat have an odor?  Feel oily?
Where do you live? (climate)
When did this get bad?
How itchy is she?