My other arm is too but not as badly.

I went out to visit Brego today and I must have brushed my arms against something I'm allergic to.

Took an antihistamine and covered my arms in hydrocortisone cream.

I think the redness has gone down.

Ah yes, the mystery brushed up on something rash

Yep. Could have been poison oak, could have been the paint on a wooden post with a chemical in it that I have a reaction to, or something like that. No idea.

Yeah, I had one of those once. We narrowed it down to "Something that grows in Fundy National Park"

LOL

I've narrowed mine down to "something at the boarding stable or possibly on the trails" because my arm started itching as I was driving home.

My first thought was the corral... I hope it clears up really soon, AND you can figure out what and WHERE you came into contact with it so you can avoid it more efficiently. ((gentle hugs)