Wow, thanks for all the info. The leather does have a darker yellowish glow under the UV light when it's cut, noticed this too. I tested rubbing my finger on both sides, no glow so far. Seems that sweat triggers the reaction. The rash on wrist was even, strap is 22mm width. The bracelet is also 22mm with same thread pattern. No rash on my right wrist, but the glow is definitely there as well. I'll read into that mimosa tree powder.