bite, bite, scratch, scratch!!!!

[choprchk]

My poor baby must be miserable! She is constantly biting and scratching. I have never seen a flea or evidence of fleas. Her skin looks great, so I assume that means no bacterial or fungal infection, most like due to the baths. I started her on ivermection around Christmas and briefly stopped in march. Then her hair began to fall out again. I'm not talking about seasonal shedding either, this is her outer coat and it comes out by the handfuls. So the ivermectin helps to a point but her scratching and biting continues. Other hair loss is seen on the tips/margins of her ears. Most of the biting occurs on her legs, back and chest, basically everywhere she can reach. No licking of the feet and she does not react to the pinnal-pedal reflex test. She's also and indoor dog so flies are not the issue on her ears.
SOME OF THE THINGS I'VE TRIED:
skin scraping(negative for mites)
bravecto(currently)
ivermectin(currently)
benzol peroxide shampoo(every 5-7days)
micronized sulfur shampoo(currently, weekly)
lime sulfer dips(every 5-7days)
happy jack kennel dip II(currently, every 2wks)
sardex II spray
zymox drops(currently)
DIET:
grain-free food(since she was a puppy, she's now 2yr)
raw chicken backs
sweet potato treats