I have been dealing with allergies for 5 years it runs in this breed. They tend to have poor immune systems from inbreeding. I have spent thousands of dollars going to dermatologist, holistic vets, chinese herbs, raw diets, specialist in blood work, two allergy blood tests and yes I am in about 6-7k on all this so here it goes. I also am on an allergy group on yahoogroups.com called allerdog and read constantly on this topic. Also have bought every animal dermatology book on ebay and read them. So I consider myself to know alot on this topic.
First you need to rule out mites like scabies and demodex so has vet done mite scraping?
Second does your dog bite at back half off dog as that is flea allergy and one flea bite can last up to 3 weeks. I personally do not use flea meds and i live in southern california and btw you live in cali and cali is the worst place to live for allergies as we bloom all year round
Next you need to have a full thyroid panel done to make sure not hypothyroid as that can cause skin issues in dogs and this breed is prone to hypothyroid and yes my dee dee is also hypothyroid and on soloxine. Hypothyroid is all a immune mediated disease - the thyroid panel is t4, t4free, t3, t3free, t4aa,
t3aa- it is a 6 panel test and it should be done by dr jean dodds who we see for all our blood work or michigan state panel as they are the most accurate-
Hemopet/Hemolife, HEMOPET a full animal blood bank, Diagnostic Laboratory, Adoption and Consultation has instructions on how your vet can send her the blood to be tested.
Next a food elimination diet and i recommend natural balance fish and sweet potato or venison and sweet potato. This needs to be done for 12 weeks nothing else no treats NOTHING. it has to be a novel protein and carb