Dandruff: A chronic noninflammatory scaling of the scalp. The absence of inflammation sets dandruff apart from other scaling conditions of the scalp, namely, psoriasis and seborrheic dermatitis. Dandruff can be confused with dry scalp. Dry scalp is caused by drying conditions. Wind, indoor heat, sap moisture from the scalp, causing flaking. Dandruff is the result of accelerated cell turnover and people with oily scalps tend to suffer most from dandruff. The dandruff test: brush or shake hair over dark paper. If you see powdery flakes, it’s dry scalp. If you see clumps, you may have dandruff.