First of all, are you sure it is dandruff, and not simply a scurf build-up from inadequate rinsing, or excess hairspray? Real dandruff is excess flakes of keratin product in self defence by an irritated scalp. A prime irritant is over shampooing with highly alkaline shampoos. The antidote is a mild acid-balanced shampoo, gently massaged into the scalp, then thoroughly rinsed away.

Medicated shampoos, or selenium-based applications, are not recommended. They can irritate the scalp further. If your problem does not respond to your own treatment or your scalp is sensitive, tender or bleeds, see your doctor.