You may have dry,  sensitive, oily or even acne and blemished skin but it can still lack hydration.  Dehydrated skin starts at a cellular level in the body.  By the time you see the problem, it's likely been there for some time already.

When skin lacks hydration, it becomes vulnerable to external stressors.  Dehydrated skin becomes thin and can cause microscopic breaks letting bacteria in.  Using products to treat and lock in hydration is imperative to healthy skin.