What Causes Chronic Hives?

I have been expereincing cronic hives ..thought it was due to food allergy that I can not determine by removing certain foods from my diet . As time goes on ..they seem to appear mor chronic ..mostly night time but yet anytime during day as well. I recently started having a hive on my tongue and then a round itchy patch on my leg. Now I am expereincing a priockly rash that if scratched will spread ..can see the bumps under skin .