What to do if i have really bad dandruff why?

Anti-dandruff 'poos: Dandruff is associated with malassezia fungus infection. Buy over-the-counter dandruff shampoos, and look for one that contains zinc pyrithione, which can reduce the fungus; selenium sulfide, which can limit cell turnover and decrease the amount of fungus; salicylic acid, which works as a sort of scrub to slough off dead skin; or ketoconazole, which works against a broad array of fungi.