Unpredictable reactions

I have been dealing with unpredictable reactions for about 3 years now.  Lately they have been getting more frequent.  At first my doctor said it was stress related, however the reactions do not occur at any particular stressful moments.  They are very unpredictable.  I experience cramping, diarrhea, hives, itchy throat, extreme itching.  Sometimes I can take atarax and it works, however when the breakout is severe I end up having to go get a steriod shot at the hospital.  Since it's obviously not a food allergy, and I'm not being stung or bit by an insect, and it happens at different times and in different locations, I'm at a loss as to what is causing these "episodes".  It's very uncomfortable, and inconvenient because both the atarax and the shot put me to sleep.  One thing I did think of is I had an angiogram around the time all this started and I was allergic to the dye....but should I still be reacting to it? PLEASE HELP!!!!!