Also, I only really started feeling brain fog when I was in my early twenties. If there were a genetic problem, would that most likely have shown up earlier? Or are there some genetic issues that manifest symptoms only as an adult?
Serious genetic syndromes can become apparent soon after birth, but there are lots of genetic, in utero, or childhood-acquired conditions that don't become apparent until after childhood.
Also randomly: I actually took Augmentin recently for what we thought was a growing sinus infection, and woke up with hives for the next several days. At the time we thought this was a newly developed penicillin allergy (I had taken Augmentin many times before), but now I wonder if this was actually a herx die-off? Can that present as hives?
I don't know if a Herxheimer reaction could result in itchy, raised hives. But it can result in non-itchy, flat red dots/blotches around the body. (which are not hives)
Hope this helps.