Question regarding health of my dog

Question
My German Shepherd is 6 years old.  I noticed he has been itching, red eyes, red bumps under mouth, dry and peeling around mouth, biting toes is how this all started.  He has scratched at one spot, back hind leg, now he has a big piece where he has rubbed his hair off totally.  I talked to vet, they say allergy, I say NO Way?  I am in desperate need of help.  I appreciate any suggestions.

Answer
Sounds like allergy to me. But GSD"s are prone to other skin conditions. What made him reach the diagnosis? Did he do a skin scraping? I have lots of things that can help you with allergies IF that's what it really is Please let me know how he reached his diagnosis.
Cindi