That is the beauty of this group as some of us have paid to get that information by these specialists and can help others on what to do so they can save on cost
Vet should have tried zyrtec first before steroids but most vets do not know about zyrtec working in dogs. Most vets just go straight to steroids just like her vet did.
She can still get her dog on elimination diet while on steroids and do this for 12 weeks as even on steroids if food is working the itching will get better and the food elimination diet and antihistamines are the first thing a derm goes to. If those do not work then they keep them on the limited ingredient diet and your choice is then hyposensitization, atopica or steroids. Going back in time I should have done the hyposensitization but I went the drug route atopica and she is so bad had to do atopica and temarilp and after a year on atopica she was vomitting so we had to do just temarilp as one drug is better than two but hyposensitization is the safest as it is natural and being in california it is worth a shot as your dog may be in the 85% of dogs it works for. 90% of the time it is environmental but if you are in that 10% where limited food works you are also very lucky
I recommend joining this group as it is all pet owners with allergy dogs as sadly allergies is a life long thing - no real cure - very frustrating and all you can do is try to keep your dog as comfortable as you can with least amount of drugs
http://pets.groups.yahoo.com/group/ALLERDOG/
atopica is not cheap either can be $100 a month