for me the diarrhea is always the last thing to happen before the itching and dizziness go away. Like you, I have episodes where the symptoms are much less intense than other times. Also like you, I've had episodes that started soon after a normal bowel movement. I've had numerous tests over the past 6 months or so (CT scan, colonoscopy, blood tests, urine tests, feces/diarrhea analysis, etc) and no diagnosis. I recently saw an allergist and she did more tests but everything came back normal and she could only say that she was puzzled by my symptoms.