Reasons for dry skin
Unhealthy lifestyles, exposures to extreme wealth conditions, bathing for long time in hot water, using harsh soaps, harsh cosmetics, can cause drying of skin.
Ayurveda's point of view about dry skin
According to texts of ayurveda, dry skin is caused by increased vat dosh in the body. When vaat dosha increases in the body, it reduces kaha dosha and makes skin dry and wrinkled.
The causes which increases vaat dosha in the body
1) exposure to cold and dry climate
2) controlling natural urges like urination, defecation, hunger, thirst etc
3) keeping awake till night
4) irregular food habits
5) consumption of spicy, dry and bitter food