Dry skin is a skin type, while dehydration is a skin condition. In both, the skin undergoes transepidermal water loss, or evaporation of water from inside the body. With this water loss, the enzymes that normally help the skin shed cells cannot function properly, resulting in a buildup of cells that makes the skin look rough and dry, contributing to the appearance of fine lines and wrinkles. Dry skin can be genetic or a symptom of systemic disease. It is caused either by the inadequate production of oil, called sebum, or by an imbalance of fatty acids, ceramide, and cholesterol in the stratum corneum, the barrier layer of the skin. Age is also a factor in dry skin. As we get older, we experience a decline in a main hormone that triggers sebum production. Dehydrated skin still produces sebum but is temporarily dry because of various factors, including environmental effects such as a dry climate or use of harsh detergents or products on the skin. It is caused by a temporary imbalance of fatty acids and ceramides in the skin’s barrier layer, resulting in a temporary spike in transepidermal water loss.