I have fine, thin curly hair that I've been coloring for years, so I picked the System 3, which is supposed to be for "thin-looking, chemically treated hair". I was initially impressed by how clean my scalp felt after the first use, and it seemed like my hair had more body. In retrospect, I realize now that it was more likely just increased frizziness from the fact that this product was frying the crap out of my already delicate hair. I noticed some hair loss as well, but according to the instructions that's a normal part of the treatment. But the worst was yet to come... After about 3 weeks of almost-daily use, I realized to my horror that sections of my hair in the front (i.e., where most of the post-shampoo scalp treatment was going) had literally broken off at the roots where my colored hair meets new, unprocessed growth. It took me a while to realize this because it seemed to happen over time rather than in one dramatic moment, but it definitely happened post-Nioxin use. So now I have a bunch of short hair on top of my head that will literally take months to grow out, plus the rest of my hair is permanently dry and frizzy-looking, no matter how many conditioning treatments I use. So, proceed with caution this system will remove scalp buildup, but may take your hair's heath with it!
