I just ran across this post while googling. I don't know if any of you still follow this thread but I just couldn't not reply after reading this discussion.
Speaking only from my own experiences, have any of you looked at some sort of "mast cell disease?" There are different variations from "mast cell activation syndrome/disorder" or MCAS/MCAD to "systemic mastocytosis." I personally have been diagnosed with mast cell disease and can see some VERY similar symptoms in reading the threads of this post. I strongly urge you all to at least research it. Mastocytosis is considered a rare disease but MCAS/MCAD seems to be a more common variation and, it seems from research, that it is probably very under-diagnosed meaning that there are a lot more people out there with mast cell disease than have been officially diagnosed.
Hives, itching, rashes, flushing, low blood pressure, tachycardia, shortness of breath, asthma-like issues, syncope, swelling, heat intolerance, headaches, body pain (bones, joints, muscles), abdominal pain, food intolerances, fatigue, diarrhea, etc. are just some of the symptoms associated with mast cell diseases.
Please, if any of you still follow this thread, please look it up! For me, getting a correct diagnosis and proper meds made the difference between being a functioning and non-functioning human being.