i have had a similar problem in a way. a rash that first i did a run of prednisone and then an anti-microbial. neither worked. valium was helpful though.

i have been looking at diet and it specifically says no to mushrooms, vinegar, yoguart, and fermented foods. when i am in flare up these foods really don't work well. (at other times they are very useful) when i am NOT in acute flare up - DILUTED apple cider vinegar topically feels good.

greens and bitters for allergies and digestion.
anit-histamine herbs maybe.
try changing diet to protein and whole grain (ask if you want recipe ideas)
include BUFFERED vitamin C - only a very little too
you could try burdock and/or cilantro if there is a heavy metal or toxicity component
if there is a nerve component you could try rescue remedy or a little bit of herb tea in food (lemon balm and oats)
an oil too like fish or vitamin e and a bit of olive oil in food

chicken and turkey are heating - in acute phase i have found sticking to cooling is much better - so lamb and beef would be good.

it is okay to fast a dog for a day and sometimes that energy towards healing instead of digestion is needed.

peace.

lisa