Most widely used cosmetic ingredient; water is almost always listed first on an ingredient label because it is usually the ingredient with the highest concentration in the formula. Despite claims of skinŠ—Ès need for hydration and claims regarding special types of water, it turns out that water may not be an important ingredient for skin. Only a 10% concentration of water in the outer layer of skin is necessary for softness and pliability in this part of the epidermis. Studies that have compared the water content of dry skin with that of normal or oily skin do not find a statistically significant difference in moisture levels between them.
Further, too much water can be a problem for skin because it can disrupt the essential substances in skin's surface layers that keep it intact, smooth, and healthy-looking. As an example, recall how skin on your fingers and toes "prunes" when you soak in the bathtub or other body of water for too long.
References for this information:
Skin Research and Technology, May 2015, pages 131-136
Skin Pharmacology and Applied Skin Physiology, November-December 1999, pages 344-351
Journal of Cosmetic Science, September-October 1993, pages 249-262