Food Allergy Rash

I started having a rash of small on my lower abdomen three days ago and the next day I had one on his lower back on the same side. I realized it arose when I tried fiber bars for the first time. The bar was, I had two days ago and the rash is still there and when I rub against it, it is very painful. How long will it take to go away and is it something other than a food allergy?

take an antihistamine or diphenhydramine HCl. or, better yet, consult your doctor, they know best.