I ve had two episodes about a month apart where my palms start to itch, I get very light headed(passed out the first time) and have some mild diarrhea. Went to emergency room. All test came back normal. My blood sugar was around 250. CT scan showed nothing and ULTA sound showed good blood circulation. I read on a forum of people with similar symptoms that some have traced it to a histamine problem. The started taking Zyrtec. Any ideas from you?