The cause of dandruff is very different from the aforementioned. Dandruff is caused by yeast which feeds on the oil on your scalp and also gorges on the dead skin cells. In other words, it is not dry scalp that causes dandruff or the two are the same condition. Dandruff is caused due to excessive oil and skin cells which facilitate the growth of the yeast on the scalp. There is a difference between dry scalp and dandruff even in their colors while they both appear to be the same.