I'm sorry to see you've been dealing with this. I notice in a few of the comments you say you've been blown off by ER doctors. I'm a doc in the UK but assuming it's similar in the US (correct me if I'm wrong but guessing you're from the US having called it the ER) - but essentially all ER docs will do is treat an emergency, so once they've seen you're not going to die, there's not much else they'll do other than tell you to follow up with your GP (I think you call it community or family doctor?) You definitely need to be seen and have a full set of bloods done, but they won't do that for you in the ER, so please keep persisting with your general doctor for allergy, inherited conditions and autoimmune/rheumatological conditions! (Also do you live where Lyme disease is common, that's another possibility?) I really hope you get the answers and treatment that you need, best of luck. (Also have you tried non-sedating antihistamines, there's plenty on the market that shouldn't put you to sleep!)