My 8 Year Old Daughter Has Had Sharp Stomach Pains

My 8 year old daughter has had sharp stomach pains followed by sudden vomiting and diarrhea and now full rash-like symptoms all over her entire torso, neck and face. This all happened about 1 hour after eating at a restaurant we have been to a lot and where she ate the same thing she always has eaten and the same thing we all ate. Not sure what to do for her. Benadryl?