Natalie, so sorry about hour hubby's mystery rash! It took me forever to realize which plants were giving me 'mystery poison ivy.' And wow, there's a lot of them. Through much experimenting and hellacious scratching, apparently I'm sensitive to some of my house plants that never bothered me before, as well as some weeds and tended plants in the landscape. Is this rash something that happened recently? Knowing when it happened could help narrow it down, and what he was doing/touching. Do you have pets? Was the rash like poison ivy?