^ what Sceptre says works.
Saw a TV experiment on the subject 20+ years ago with a girl with llong black hair. Looked OK when she started, looked awful and itched badly (maybe where Sceptre's conditioner comes in) after a couple of weeks but when she did the reveal after, I think 10 weeks, the effect was amazing! Gasps from the studio audience and the hair was absolutely stunning with a lovely sheen and not greasy or itchy.
If you have the patience and social acceptance by others, try it....if not Head and Shoulders works for me - doesn't totally eliminate it but keeps it under control