Ok so if she has food allergies, she will be allergic to regular dog food ingredients like chicken, beef, lamb, corn, wheat or barley. She may be allergic to more than one ingredient or just one. Cheap dog foods use corn as a filler which is highly allergenic. I know beneful and pedigres have a lot fo corn in them as well as meat bi-products which are left over parts and not real meat.
So, you can try an over the counter diet, from the pet store, that says "for sensitive skin" on the label. I use "proplan sensitive skin and nutros sensitive skin for my dogs." They have fish as the protein and oatmeal as the carbohydrate. They also make treats for sensitive skin.
"Wellness" make limited ingredient diets which only have 2 ingredients. You can get all of the brands I have mentioned at PetSmart pet store.
Your vet can prescribe a prescription completely hypoallergenic diet for a 6 week diet trial. There is also a blood test that can be done to see what she is allergic to.
She could also be allergic to something in the environment such as grass, dust mites, or pollen. The blood test also tests for environmental allergies.
If she were tested for allergies, allergy "shots" could be prescribed to desensitize her to the allergens.
To help with the itching, you can try 35 mg of benadryl every 8 hours.
You can also try 1/2 of a 10 mg zyrtec tablet once a day.
Both of these are antihistamines and can be purchased at any drug store.
You can spray hydrocortisone spray on the affected areas 3 times a day.
If you rub her ears, and her hind foot starts going, she may have mange. The ear rub is a crude test. A vet would have to do a skin scrape, of an affected area, to determine if she has mange. If she does, she can be given an oral medication to kill it.
Once she stops itching so much, the smell should resolve.
www.VeterinaryPartner.com/Content.plx?P=A&A=599 more itch relief remedies