Dry skin is either a skin type or a temporary condition. Skin tends to become drier with age, but dryness can also be triggered by diet, lifestyle, and environmental factors.
Skin is the largest organ of the body. It's easy to overlook skin as an active organ, since it's so good at its job. The skin's biology has evolved over thousands of years to keep hydration locked in. The human body is made up of over 60% water, so a healthy skin barrier is critical to survival.