Oils and creams, or even dandruff have no role to play in the growth of the hair. If any good branded product is used, it usually does not do any damage to the hair. Dandruff per se is harmful. If you have persistent dandruff, use a good medicated shampoo with Ketacenazole (available in brand names of Scalpe, Arcolane, KTC, Nizral) which will help eradicate dandruff. Use it as often as required till dandruff goes away.