I wonder if the rash isn't Prickly Heat? When I used to get heat rash, an area, or sometimes my entire back or flank etc. developes hard pimple like, raspy hard bumps, like tiny plugged volcanoes, that itch like crazy. When I most often joined 15,000 close friends, on a cross Iowa (@ 500 miles) mid summer, week long bicycle rides or such. The cure was baking soda, sodium bicarbonate. Either rubbed on dry or sometimes, applied as a water based paste, the pimple like bumps react by weeping something thick and sticky, reducing the pimple looking bumps. An hour after, the rash had mostly resolved and a day later after three or so reapplied baking soda sessions, the rash, supposedly clogged sweat glands and possibly "oil glands" gushed sweat and metabolic toxins in the continued hot, humid hilly Iowa bicycle ride. As a tween, I took at least one and sometime two very hot, very long showers. Sometimes I suddenly would go weak in the shower and would sit down until the feeling went away. The possible souce, was dehydration and hydrating with kool Aid spiked with electrolytes, ended that problem. Still sometimes when I overdid it, maybe showering soon after exertion or being out in the heat and coming in for a shower I got prickly heat. Hope this helps.