We just got back home from visiting Arizona (Gold Canyon at the base of Superstitution Mountain, so in what's known as the Sonoran Desert) and my ILs home there.
It's near a golf course and a small wash.
DH and DS went for a walk near both and a day or so later they both had bright red splotches on parts of their bodies.
DH has two spots on his hands and DS has two spots on his upper lip in the shape of his little fingers (like he wiped his fingers on his face and left a mark).
As days passed (maybe a week), the deep red became inflamed and then blistered like one might see with a severe sun burn. Neither have complained of any pain or burning with the spots.
I know this is from a plant and we know it came from their walk. It has not spread to anyone else, nor has it spread on their bodies.
Any ideas what the plant could be?