When the upper layer of your skin, known as your stratum corneum, is lacking in moisture, this is known as dehydrated skin. 

This is different to having dry skin. Dry skin is a skin type, while dehydrated skin is a skin condition and can be treated.  

Our skin loses water every day naturally, but if it is losing more water than it needs to be healthy, then signs of dehydration will appear. 

Dehydration is caused by external factors like diet, caffeine consumption, not enough water and the weather. It will feel tight, look dull, may exaggerate fine lines, cause dark under-eye circles and even trigger breakouts and inflammation. If this is not your normal skin condition - they likely, you are dehydrated.