My name is ***** ***** I’ve been involved professionally with dogs in the health and behavioral fields for over 18 years. It will be my pleasure to work with you today. Your question went to the vet only side of the system and was just opened up to the pet expert side where other non vet verified experts can answer which include vet assistants, technicians, etc.
I totally understand what you are going through. Unfortunately, in cases like this, your vet treats the skin dermatitis with steroids and antibiotics, sometimes shampoos, but never addresses the underlying allergy which causes the skin issues. Food trials can be done, and this is effective when a food switch triggered the skin issues to begin with. I personally think that allergy testing, while expensive, is cost effective since then the allergen can be avoided or the dog desensitized to the allergen.
With a limited diet food, it first needs to not contain the allergen. The second thing is it has to be a food allergy. If it isn't a food item, a food switch won't help. It might be a pollen, cleaning supply or even a type of grass. There is a medication that seems to help when the allergen is one that can not be avoided. It is called atopica. You can read about this here:
You will need to clear up the dermatitis one last time but the medication may help keep it from occurring again after that.
I hope this information is helpful to you. If you would like any additional information or have more questions please don’t hesitate to press the reply to expert or continue conversation button so I can address any issues you still have . If you do find this helpful, please take this opportunity to rate my answer positively so I am compensated for my time.