question: Hello, my 10 yr old son with no immune issues has developed a rash . It came on very suddenly on lower legs, then traveled up legs, arms and buttocks . No groin rash or face. We changed to nature clean scent free detergent thinking our other soap might be the culprit but to no avail. Today he has a low fever off and on. Also had two periods several hours apart complaining of sharp pain in his ribs. The pains last about 10 min and are gone. Tried benedryl but didnt change anything. Rash not overly itchy.. red and raised... No blisters.