I made the fatal error of attempting to bleach my own hair from dark brown, to white blonde.
Hairdressers among you may wince, and you'd probably be right to. I went through 3 lots of bleach (ouch) and while my roots were lovely and white, my ends were yellow. I bought some rather expensive purple toner, and it made hardly any difference. I was about to dye it back, when I saw this product. It is fantastic. After a couple of washes, the yellow tones are all gone, however, it has started to take a slightly lilac look (due to my overuse!) so I'm giving it a rest.
Bottom line, it's a life (and hair) saver.