Which substance is not absorbed by the skin?

• A. Water
• B. Vitamin E
• C. Vitamin C
• D. Vitamin A

Answer: (A)

Understanding how the skin takes things in hinges on its barrier nature. The outer skin layer is lipid-rich and designed to limit inward diffusion, so substances must have the right properties and vehicles to penetrate. Water, even when applied abundantly, does not cross intact skin in meaningful amounts; it mainly stays on the surface or evaporates, which is why moisturisers focus on locking water in rather than delivering it inward. Vitamins, when formulated in suitable carriers, can be absorbed: Vitamin E and Vitamin A are fat-soluble and readily move through the lipid barrier in oil-based or compatible formulations, while Vitamin C can be taken up by the skin in properly stabilized, well-pH-controlled products. Therefore, water is not absorbed by the skin.