18 yr old son, yesterday had aches & low grade fever, took generic tylenol. 4am fever gone, but had rash on lower legs, extremely itchy, took benadryl which helped, that rash went away, rash then appears on inner arms - had him shower incase it was something he had touched. Nothing new as far a detergent, foods, soaps etc.. rash on arms mostly gone, but now all over upper shoulders, creeping up neck - benedryl again for itch. No other symptoms, no dizzyness, no trouble breathing - any reason to worry?