My hairdresser put me onto it after she had a Nioxin night at the salon that I missed and apparenty the rep used a microscope on her scalp and showed how blocked and filthy her hair folicles or whatever they are were. So what Nioxin does is cleans it all out and this encourages growth of new hair and also repairs the hair shaft. But as I said in a prev post, you must use the scalp spray treatment after each shampoo and condition. My hair was really short and I grew it out so quickly. I really noticed my hairdressers hair every six weeks and I had to look closely to be convinced she didn't have hair extensions or a wig cause it got so long in such a short time.