Strange Rash

I feel rather fed up at the moment. For years now I have had a recurring problem, an inexplicable complaint that has been described by the medical profession as ideopathic. That mean that they have no clue as to what is the cause and therefore can offer no treatment.  It is spasmodic and I can go up to  year without any occurence, but now it is back.  It starts, almost always, as a small red patch in the centre of my left palm. It itches like crazy and then rapidly spreads to both hands and often the back of my scalp. In really bad outbreaks my body gets covered in hives and nothing I can do makes any difference. I have tried quadruple doses of powerful antihistimines and they just seem to make it worse, so I just have to ride it out, hoping that it will recede soon. I also feel unwell in a way that is so hard to put into words. The itching palms is awful and keeps me awake at night, but the worst thing is when it spreads to my feet. Thankfully they are pretty well itch free right now, but I dread that coming back.  The itching is strange and subcutaneous and always gets worse at night. Last night I was up every hour, more or less on the hour, running my hands under the cold tap, and as a result I am also sleep deprived.
I have had allergy tests and they prove negative, and I can see no external event that could act as a trigger. So anyway I feel pretty crabby