Vitamin D is made in the skin in response to sunlight, so one question we might ask is whether vitamin D might also somehow promote skin health. One piece of indirect evidence that supports this concept relates to the experience that many sufferers of the skin condition psoriasis have in the sun.
Psoriasis is characterized by raised, red, usually scaly skin “plaques” (often on the knees, elbows, and scalp). Quite often, these can improve considerably and may even disappear when exposed to sunlight.