I Have Had A Rash On And Off Since Last

I have had a rash on and off since last October. Came on suddenly. Tiny light colored bumps....not blisters. Mainly on my back and upper arms. Itches terribly. I start itching and almost can’t stop. I scratch til they bleed. Stopped eating for two days, got better......stopped eating gluten......sugars......can’t eat dairy. Helps for awhile and they are back. Tried candida cleanse......detox.....hmo Dr. didn’t seem to worried. Can you help me.