Well I first tried Rogaine a year back it was the worst in terms of Itchy scalp & dandruff problems, I have now used doctor Lee's with & without propylene glycol, I always felt even with using lee's standard #500 there was always a bit of itch & irritation, Fair Tax how is spectral in terms of irritation & itch. does it have a lower concentration of PPG then Lee's ? anyone else care to chime in . Thanks again.