AKA dry combination skin, oily dehydrated skin, Introduction Most people confuse or misdiagnose their skin between dry and dehydration. Dry skin can be generic and is normally caused by not having enough sebum in the skin, while skin dehydration is from not having enough water. Skin dehydration happens when the outermost layer of the skin starts to evaporate moisture, and insufficient internal hydration of epidermis. Once this damage occurs, the skin will no longer be a good barrier and causing skin problems such as scarring, taut skin, superficial lines, skin lack of radiance, loss of elasticity and premature aging.