I too experienced hives for many years. What ended up being the cause was something very simple - red dye. I was allergic to anything that contained any amount of red dye. My biggest problem was that I was taking tegretol (eplilepsy medicine) which was pink. It contained the dye and this was why every day and night I suffered through these. My doctor advised me that even if a medication is not pink or red in color it can still contain red dye. I was lucky, I had my medication changed to something without red dye, and whenever I eat anything that has red dye in it I just take benedryl - the kind that is dye free. The tablets are clear. Don't know if this can help but perhaps it could be something this simple.