What characterises dry skin?

Feelings of tightness, discomfort, a dull complexion and fine lines due to dehydration: dry skin is lacking in water, or lipids, or both at once. It is less well protected and so reacts more to external aggression (pollution, climatic conditions, air conditioning, etc.). It also has a tendency to wrinkle more quickly, especially inasmuch as the skin naturally becomes drier as the individual ages.