Directly the scalp condition is not a cause of Dandruff but yes they can certainly aggravate existing Dandruff. Excessive oily scalp may result in accumulation of dead cells and formation of big clumps of flakes which are greasy in nature. Dry skin is also commonly associated cause of dandruff which is flaking in nature. Here flakes are smaller and dry in nature. Though certain studies show that dry skin is not cause but instead it aggravates the Dandruff.