That's interesting about apple cider vinegar. I think vinegar does give me a reaction- hives and itchy rashes and strangely my ear can swell up and turn red. I linked it to mint sauce (contains vinegar)which I ate usually on a sunday and then my ear would be swollen on the Monday. Mayonnaise can also do this to me too. There is also information on histamine intolerance on the Allergy UK site.