You have not listed what kinds of allergy testing that your veterinarian has performed. For environmental allergies there are blood tests and intradermal skin tests. There is no
reliableReliable gentle laxative test for food allergies. I do not know what
substancesDrug abuse your dog has been tested for. There are no tests that test for all
allergensAllergen
Positive reaction to allergen. Dogs can be allergic to anything. When a dog is as severe as your dog seems to be I look for secondary
factorsFactor ix complex. Secondary factors include: Ectoparasites (skin parasites) such as scabies, demodex or other mites, or fleas; or, skin yeasts (malasezzia), or ringworm; or, autoimmune factors; or, endocrine diseases; or, pyoderma (bacterial skin infections). Much of the time all of the factors have to be controlled to achieve complete resolution of the skin problems. If your veterinarian has not done so already he or she should do a skin scraping, impression smear, slide of the discharge from the ear, or biopsy of the skin lesions. He should then treat for whatever secondary skin infection he finds. Blood tests are necessary to diagnose endocrine and some autoimmune disease. Treatment can involve: shampoos, topical rinses or conditioners, topical ear medication, steroids, antifungals, antibiotics, antihistamines, hypoallergenic diets, antiparasitic medication and a new medication called Atopica depending on what your veterinarian has found. The new drug Atopica is very reliable for canine atopy, but only if the secondary factors are controlled. I mentioned food allergies earlier. To test for food allergies your veterinarian would have to place your dog on a hypoallergenic food such as venison and potato or duck and potato as a food trial. Your dog cannot be allowed to cheat at all for 12 weeks while on the food trial. In other words, no treats or flavored heartworm pills are to be given during this time. After the 12-week period you introduce a small amount of your dog’s old diet and wait one week. If the symptoms come back you will know that your dog was allergic to one or more of the components of his old food.
I hope this helps a bit. Thanks!
Dr Cheng