The root causes of dry and dehydrated skin are fundamentally different. Dry skin is a skin type that naturally produces less sebum (oil). This can be due to genetics, hormonal changes, or aging. External factors like cold weather, low humidity, and the use of harsh soaps or cleansers that strip the skin's natural oils can also cause or worsen dryness. Symptoms of dry skin often include a feeling of tightness, a rough texture, flakiness, peeling, small pores, and sometimes itching or redness.

Dehydrated skin, conversely, is a temporary condition caused by a lack of water in the skin's uppermost layers. Common causes include not drinking enough fluids, excessive sweating, a diet high in caffeine or alcohol, and environmental factors like sun or wind exposure. Even using harsh skincare products can disrupt the skin's barrier and lead to water loss. Signs of dehydrated skin include a dull, tired appearance, more pronounced fine lines, reduced elasticity, and dark under-eye circles. A unique sign is feeling both tight and oily at the same time, as the skin may overproduce oil to compensate for the lack of water. It is also possible to have both dry and dehydrated skin simultaneously. In this case, the skin lacks both oil and water, requiring a comprehensive approach to replenish both.