What is the difference between dry and dehydrated skin?

Dry skin usually refers to skin that produces less oil, while dehydration refers to a lack of water. In practice, I care less about assigning a perfect label and more about correcting the combination of oiliness, tightness, flaking, and comfort that is actually present.

Oil and water are different issues

Oily skin can still feel dehydrated. Pore size or fine lines alone cannot reliably separate the two, so look at oiliness, tightness, flaking, and how your routine feels over time. The useful goal is comfortable hydration without unnecessary heaviness or irritation.