You're kinda doing things backwards. Taking things out one at a time, rather than starting with one or two ingredients and adding in.
When the body is in an allergy state, it is prone to develop more allergies, so you don't want to be feeding an allergen with things that aren't if you can help it.
I haven't been following closely, but likely this needs a combination of things - taking out offending foods, adding supportive nutrients, and fighting the rash with whatever it needs (abx, acv, shampoos, etc.).