A few years ago while we were in Italy I developed a rash on my legs, it looked awful, but didn't hurt. It seemed to be the sun that was causing it, even though I was wearing trousers. Then later in the week I developed one on my chest. I did see the GP, but he didn't know what to make of them, probably told me to come back if it didn't clear.
I think I may have been taking sulpha at that time.
Lyn