A common cause of dandruff is yeast which lives on everybody’s skin. Sometimes, if you’re using certain shampoos and they’re not working it’s possibly because your scalp needs something else. Try shampoo with an ingredient such as ketoconazole or salicylic acid in it and be sure to massage this into your head. Doing so should help decrease both the amount of flakes produced by the dandruff and also provide relief from irritation caused by dryness.