Hi Darren,
I saw your post about Cold Urticaria and wanted to reply since I have a son who has developed this recently and I've tried to research it as much as possible. It can be dangerous if you have sudden big changes in temperature, for instance when swimming. You should never swim alone and you should have an epi-pen. My son had an anaphalactic reaction when he went in the ocean this summer - trouble breathing, arm swelled up, passed out, threw up, etc. There is not a lot of knowledge about this out there, so good luck. We have him taking Allegra in the morning and a prescription anti-histamine at night (xyxol) plus 300 mg of ranitidine (it's an antacid that also works like anti-histimines do.) But we're still waiting to see how effective this all is.
Best wishes-
Carroll