It turns out I’m not allergic to nickel as originally suspected, but I AM allergic to formaldehyde resin. It seems to be most commonly used in industrial adhesives, for bonding fabric and leather to vinyl (ie in my shoes) and in 3M micropore tape.
It still doesn’t explain why I haven’t been able to wear earrings for the last 18 years, does it?
Oh well, you close one door and open another, I suppose.
Now I have this red square on my back that I plan to itch for awhile, if you will excuse me….