I had twice taken Benadryl for lack of anything else I had on hand until I got to a doctor, but the reaction would start fading before I'd get there (I'm quite a procrastinator). For the last few years, I have kept an EpiPen at home, which has to be injected before you head to the ER. It has Epinephrine, probably the same thing they use in the ER. I have no clue what it was. I am sure it was a delayed reaction to something (kind of like your PI thing was), either something I ate earlier or maybe something I'm not usually in contact with. My sister has a very bad anaphylactic reaction to any place that's had rats around, so that's something I might get checked for eventually. I've been checked for the common type of allergens and had 3 mild pollen allergies, but nothing strong enough to cause an anaphylactic reaction showed up.
