Quote Originally Posted by Hyacinth View Post

Diet adjustments means finding out what a dog is allergic to, by doing elimination diets.
Start with most likely eg Gluten, so feed a rice based food or no wheat/oats/rye grains.
see if that makes a difference (might take a couple of weeks to know)
then try eliminating stuff like corn
then try different proteins - this is harder for dry food as a lot of them are very vague about what protein goes in eg "meat meal" will not help if your dog happens to be allergic to the variety that they use. Or they change what they use.

If it was my dog (and I have recently been in the "OMG the dog won't stop scratching" stage). I would;

Put it on cooked chicken and rice for a bit and get see if that helps. If it does - your problems are probably diet based. Slowly re-introduce foods one at a time and keep an eye on reactions. If not - blame the environment.

Do other things as suggested above + wash / replace all bedding.
Look at bedding - what is your dog sleeping on? The majority our dog bedding is cotton or wool or towels. Washed very often in sensitive washing liquid (no perfume, low allergen) and HOT water.
Flea bomb the house (even if you can't see fleas)
Wash your kennel out with warm soapy water
get some fresh air and sun into your dogs environments.

Good luck. Having recently been through itchy, smelly, fussy dog territory I feel your pain.