Well, after one trip to the GP, one trip to A & E for a bit of trouble breathing and swollen hands and feet, and multiple trips to the pharmacy, I seem to be doing a little bit better today. I've been on antihistamines since Friday, guess they are building up in my system and working a bit. I noticed that I was itching a lot after I ate some bread last night (maybe a coincidence) so I didn't chance it and just got some gluten free soups and rice to eat and I've been drinking lots of organic chamomile tea and lots of bottled water. Tepid baths and calamine lotion have helped a lot. I also found Kingsley House anti-itch cream which has chamomile and urea in it and that seemed to help soothe my skin a bit.
Today, I actually managed to wash and dry my hair, get dressed and buy a few groceries which was a massive improvement considering I hardly got out of bed for the last three days except to jump in a cold shower and I spent my waking hours crying from misery. Yikes. Pretty serious stuff, I wouldn't wish it on my worst enemy!
But it seems to be fading a bit and is significantly less itchy than yesterday, so hopefully I am on the mend. (Though when I woke up, I had a few spots on the soles of my feet which doesn't feel great.) I still slept all afternoon, but at least I managed to get out and about. Thanks for the advice, everyone. I'm hanging in there.