What Causes Stomach Ache, Diarrhea And Itchy Rashes On The Body?

Yesterday, while reading a book after work, my stomach began to hurt, I had diarrhea, then broke out in an exceedingly itchy rash, which spread rapidly all over my body. I went to the minor medical clinic, where they gave me a steroid injection and called an ambulance. They mentioned that I had tachycardia and wheezing was noted. When the ambulance arrived, I was given epinephrine, albutorol breathing treatments and benadryl administered through an IV. This has happened only once before, exactly 6 months ago, and my airway was restricted. Was this anaphylaxis (sp)? and what could cause it if there were no environmental similarities between the two events? The only food I had yesterday was a hamburger, which I probably eat once a week.....no change in soaps, etc, no medications, no bug bites....