Hi Bigdreams, sorry it's taken me a while to respond to this thread, but I was very interested in your description of symptoms.
To cut a very long story short, my own main symptoms include a generalised sensitivity (not allergy) to a wide variety of foods, and a more general sensitivity and itching which comes and goes. Fairly recently I've found that the two are related, and that when my digestion is bad, my sensitivity and itching is as well.
However my itching is nothing like a 15-20 minute reaction, the sensitivity is pretty much constant although it fluctuates in intensity - but it is certainly worse just after I eat something I shouldn't.
I get no rash whatsoever with my itching, which my doctors all say is "impossible", and proves it isn't an allergy. So I think the first question I would be asking is whether you get a rash anywhere when this itching flares up - if so, maybe it's a conventional immune response.
Although you say that eating pretty much anything provokes this response, it still sounds worthwhile experimenting to try to find something that doesn't. For me, literally the only foods I am confident in are potatoes, beef, broccoli and most fruit. That's the lot: pretty much everything else I've tried provokes a reaction.
Another thing to consider is organic food: pretty much everything we eat these days is shot through with pesticide residues and chemical additives, so if you were highly sensitive to them, it would seem like all food was bad for you. If you haven't seriously tried organic food, I'd strongly recommend it - I can really tell the difference in terms of response, and by the way, I'm talking about organic produce from a health food shop there, not 'organic' food from a supermarket, which I don't generally get much benefit from at all.
There are quite a few people on this board who have the same "impossible" and "unheard-of" itching reaction as I do, and we all seem to have a lot in common; so far your description sounds a little different to me, but it could be related. I'd be interested in a little more detail about the rest of your symptoms.
I think if there was a single piece of advice I would say about all this from my own experience, it would be that all environmental challenges, whether they be food or external factors like mold, seem to be cumulative in relation to my own sensitivity, so I would personally recommend going to war on all those sort of factors - which include things like washing up liquid (I react badly to non-eco liquids, and something like that could even be there as a residue on your plate and cutlery by the way!), cleaning products, environmental mold etc etc.
Basically in a nutshell, switching to a much more 'green' lifestyle made a huge difference to me...hope you find something that works for you.
