I am experiencing it right now for the past 5 days and I'm 10dpo. I'm also autoimmune. With my first pregnancy with my son I developed pupp (can't remember I there's another p!) and so I think it's possible. Anything can happen. I'm not looking too far into it- I just know its strange and annoying. This is the first time this has happened in 2 years since TTC and I've not changed anything I use- we mainly use dye and allergen free items anyway. Btw I know this post is old, but just wanted to share!
Maybe you are allergic to something. There is no reason to get hives while waiting to see if you have conceived.