For Skin, Hair, Nails and the Immune System Selenium is a very important trace element for metabolism. Vitamin C and E as well as zinc and selenium help to protect cells from oxidative stress. Selenium, Vitamin C and zinc together with Vitamin A contributes to a normal function of the immune system. Vitamin A contributes to the maintenance of normal mucous membranes. Zinc contributes to the maintenance of normal hair, and together with selenium, they contribute to maintaining normal skin and normal nails. Vitamin C contributes to normal collagen production for the normal function of the skin.