It seems I may have a reaction to ivy. I have identical rashes on both wrists which may be a result of climbing sycamore to lop branches.
I have other posts that refer to this rash
1. http://rogerlovejoy.net/blog/blush.php/2017/07/08/wrist-inflamation
2. https://calstock.org.uk/parasites
and here are a couple of links to the ivy issue
1. http://www.dermatologist.org.uk/poison-ivy-rash.html
2. https://en.wikipedia.org/wiki/Urushiol