Everything you were given was a band-aid
You did everything you were told. Here is why none of it held.
Allergy pills (antihistamines) mop up the histamine after it is already out. The alarm cells keep firing, so the dose keeps climbing.
Creams and oatmeal baths calm the patch you can see. The patch is the end of the reaction, not the start.
Elimination diets hunt for a food trigger. If there were one, you would have found it by now.
Steroid tapers work while you are on them, then it comes back the week you stop.
Every one of them works on the skin you can see. None of them reach the cells that start it. That is the whole reason it keeps coming back.