Excessive dry scalp is caused by a deficiency in oils secreted by the sebaceous glands on the scalp.
Harsh Shampoo
Many shampoos that are heavy in detergents and chemicals can remove too much of the scalp’s natural oils.
Diet
A diet deficient in fatty acids or abrupt and extreme changes to eating habits, as those associated with crash or fad diets, may cause scalp dryness.
Dehydration
Not drinking enough fluids or over-indulging in diuretic beverages can cause an excessively dry scalp.
Hard Water
“Hard” water, or water rich in mineral content, may also contribute to dry scalp.
Air Conditions
Dry air in the winter, in addition to conditioned air from vents, may contribute to scalp dryness.