First, I would suggest you see a Doctor of Neurology(spelling) and Dermatology.
This is probably totally unrelated but I have a question and then an explanation of the question for you.
Does it happen anywhere from 30 minutes to 2 hours after a morning shower perhaps? Also, does it ever happen in just spots like perhaps your hands when you wash dishes?
The reason I asked is because several years ago, I had very similar symptoms,full-body flushing in patches all over after showers or on my hands after washing dishes or bathing the kids.
Also had hives when I touched anything cold,and trouble breathing,when I ate or breathed, anything very cold.
I was at a loss and went to a Doctor of Neurology and Dermatology and found that for some unknown reason to them I had developed two conditions, cold urticaria and Aqua urticaria..which are both very unusual.
Basically means you are allergic to cold and to water and can be dangerous in certain situations.
Like I said, This is probably unrelated to what you have, but I figure any idea thrown out there might help someone!