Does your vet think this is allergies?
Do you know the name of the medication that worked?
Thanks for answering my questions.
As the owner of not one, but two allergy dogs, I can completely understand your frustration!!
With my one of my dogs, the one with the worst symptoms, I had my vet do VARL testing (more info here: http://www.varlallergy.com/ ), which determined exactly what he was allergic to (turns out he's allergic to ragweed and a specific type of pollen), which made it easier to control his contact with the items he's allergic to. As a side note...many, many, many dogs are highly allergic to corn and corn products, so it could very well be that the corn she's been nibbling on is the source of her allergies.
We also began using the medication Atopica (more info here: http://www.atopica.com/ ), which helped control his itching and made him a happier guy. Atopica is sort of the 'big gun', and once we got my dog's allergies under control, we were able to switch to Temaril P instead (which is less expensive and it only takes 1/4 tablet once a day to keep my dog's allergies in check). Obviously since your boy has had reactions to steroids in the past, you won't be able to switch him to the Temaril P, but the Atopica doesn't have steroid in it, so it may be a better option to try.
I also understand how expensive it can be to treat allergy dogs. Luckily, there are some organizations that might be able to help. If you'll follow these links: http://www.speakingforspot.com/helppayingforveterinarycare.html , http://www.theamericandogmag.com/non-profit/resources-veterinary-bills-financial-assistance, you'll find dozens and dozens of organizations that may be able to help pay for you to take your dog to the vet. Also, there are some clinics who offer free exams and other treatments and require that you only pay for medications. If you'll follow this link: http://www.vcahospitals.com/main/offer , you can see if there is one in your area
My suggestion is that you call your vet and ask if they think VARL testing and Atopica is right for your dog.
I hope this helps!!