Red food dyes

My daughter went to Vacation Bible School for the first time ever on Monday.  When I picked her up, her eyes looked a little red to me.  Half an hour later, even more so.  Then I noticed a small rash on her arm.  I gave her some Benadryl, and she went down for a nap.  About an hour and a half later, she was covered in hives.  Her arms, her legs, her hands, and her cheek all had red welts.  I called her pediatrician, who sent us their Urgent Care.  They have pinned her reaction down to Red food dye.  Have any of your children, or anyone you know, had a similar reaction?  If so, I'd love to hear if they had a reaction a second time, etc.  I consider myself to be pretty conscious of what my daughter eats & drinks.  When she had the fruit punch at VBS, it was the first time she'd ever had fruit punch.  I buy a lot of our packaged food (cereal, cereal bars, toaster pastries, and so on) from Trader Joe's, most of which is dye-free, all-natural, etc.  This means that I'm not too concerned about changing what we eat to accommodate a red dye allergy, BUT I need to know if small doses in snacks at preschool or a cookie from the grocery store will end up hurting her.  Does anyone have any advice?