Dry Scalp Underlying Cause
A fungus, called Malassezia, is normally present on the skin of the scalp. Occasionally, the fungus feeds on the oils in the scalp and grows out of control. This causes shedding of the skin cells on the surface of the scalp. The skin cells clump together to form white flakes. The cause for the overgrowth of fungus is not known.
Dandruff is more common in the following situations:
- Periods of stress
- Oily skin
- Poor scalp cleansing
- Georgalas A. Enhanced delivery of an anti-dandruff active in a shampoo vehicle. J Cosmet Sci. 2004;55 Suppl:S207-14. 
- McGrath J, Murphy GM. The control of seborrhoeic dermatitis and dandruff by antipityrosporal drugs. Drugs. 1991 Feb;41(2):178-84. 
- Pierard-Franchimont C, Hermanns JF, Degreef H, Pierard GE. From axioms to new insights into dandruff. Dermatology. 2000;200(2):93-8.