Water

The most widely used cosmetic ingredient

Typically appears as the first ingredient in skin care products

Only a 10% concentration is needed in skin’s outer layers for softness and pliability

Studies show dry skin and oily skin do not have a significant difference in moisture levels

Water is the most frequently used cosmetic ingredient. Water in skin care products is almost always listed first on an ingredient label because it is usually the ingredient with the highest concentration in the formula. Water’s primary function in skin care formulas is as a solvent.

Despite claims of skin’s need for hydration and claims regarding special types of water, it turns out that water for skin may not be as an important ingredient as commonly thought. Only a 10% concentration of water in the outer layer of skin is necessary for softness and pliability in this part of the epidermis, known as the stratum corneum. 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 “prune” when you soak in the bathtub or other body of water for too long.

See: Natural Moisturizing Factor (NMF), Deionized/Demineralized Water, Purified Water, Aqua/Water/Eau