I got mine from giving my horse Trimethoprim/sulfa and might not have figured it out if my husband didn't know about his sulfa allergy
already. It started with hives and
puffy eyelids (presumebly from hives), and
pain in my elbow I thought was from having it in the same position at work all day. I also had a half dozen huge bug bites with 1/8 pus filled tops. I then started getting knots (which I thought were also bug bites at first). My other joints seized up and I got more knots.