Small hives all over my body... What could be the cause?

Hello everyone.

Yesterday I broke out in hives and it has only gotten worse since. I have no clue as to what could be the cause, but I have never been allergic to anything before, and nothing like this had ever happened to me in my life. Yesterday I had some honey-flavored yogurt with shredded wheat inside, then at work, for lunch, my coworker and I had a Thai Chopped Chicken Salad from Panera Bread. Even though this salad contains things such as nuts, curry, edamame, and other exotic ingredients, I had eaten it at least 15 times before with no allergic reaction whatsoever. However, half an hour after lunch my arms and head started itching, then my back, chest, and abdomen. Little red bumps started appearing all over my skin. My mom suggested that I drink some milk just in case it was a food intoxication, but that did nothing. During the next 3 hours, things just got a whole lot worse. I had itch attacks (mostly on my back). I felt horrible and helpless. When I finally finished work and got home, I took 2 Benadryls and slept. Then took 2 more Benadryls about 5 and a half hours later and slept again. I woke up today covered in these little hives, even my face. Can anyone please shed some light on this? I'm including links to 3 images of my arms and stomach.
Thank you so much in advance.

-Marie

Pictures:
http://i52.tinypic.com/10fnb84.jpg
http://i52.tinypic.com/2qcduo3.jpg
http://i53.tinypic.com/2d0exvt.jpg