I've been going through this since last summer. I've finally pinned it as flea allergies. We did 3 food trials (all 3 months long) and no change. You could try washing her bedding and clothes in Tide free or something without fragrance or dyes, just to rule that out. Make sure your home is free of dust and vacuum frequently. Mitzy is on a flea preventative called Comfortis and WAS being given it every month. We also have the house treated once a month. I NEVER found a flea on her once we switched to Comfortis but she was still getting bit. I learned it only takes one bite to set off an allergic reation, and its a fairly common allergy especially your dog has ever had fleas before. My vet suggested we put her one the Comfortis every 3 weeks instead of every month and isince then we've had no itchies.
May I ask if there's a generalized area where she's itching? Mitzy was itching her face and armpits NONSTOP day and night. They say flea allergies are usually itchy by the rear end and face but she never itched her rear end. It was confusing because all signs pointed to food and it ended up being fleas.
I'd suggest treating your house for fleas and vacuum at LEAST once a week. Get her on Comfortis and a food with a single protein source (a protein that she's never been exposed to) I'd suggest Wellness Core Ocean, Natural Balance Fish, or we tried Taste of the Wild Bison and it worked great.
Hope some of this helps..
__________________ Jess  Mitzy |