I’m posting this here instead of GQ, since there can’t possibly be an actual answer, only an informed opinion. Anyway. . .
This wasn’t mine, and it was successfully treated, but the patient didn’t ask a lot of questions.
Anyway, I have a friend (seriously!) who had a rash that oddly showed up in two unrelated placed: Her face broke out in a rash and actually puffed up a good bit (eyes almost swollen shut), and there was another rashy place on her thigh.
Coincidentally, or not, this occurred after she had an unrelated injury working in a restaurant. She had cut her hand or finger, and had first gone to the doctor about that. The rash showed up a day or so later. Doctor said “spider bite”, and that was the end of that as far as my friend was concerned. She got the prescription, and it cleared up pretty quickly. [And I do not know what the medication was.]
Since I have no medical or entomological background, I didn’t feel I had any place in pointing out that might not have been accurate–but I personally was skeptical. I was more inclined to believe that she was exposed to some pathogenic bug when she cut her hand in the restaurant. . . but, again, that might have been coincidence.
One wild thing about her rash–after the swelling in her face receded, the skin started flaking off exactly the same way it does after a sunburn.
A “real” answer to this is obviously elusive, but I would still invite any informed opinions on what might have been the origin of the rash.