Vitamin D (Vit. D) Is a fat-soluble substance. Humans get it endogenously on exposure to ultraviolet radiation or exogenously via its intake in the diet. It has a known role in homeostasis of calcium, mineralization of bone, immunity modification, and cell differentiation.
There are two types of vitamin D: vitamin D2 (ergocalciferol) that is found in plants and yeasts, and vitamin D3 (cholecalciferol) that may be found in animal sources or multivitamins. However, ultraviolet (UV) radiation from the sun causes the molecules that serve as precursors in the skin to take in vitamin D3, which accounts for 80–90% of the body's storage, then it will be hydroxylated in the liver to 25 hydroxyvitamin D and further hydroxylation will occur in the kidney in order to form 1,25 dihydroxyvitamin D. At the end, Vit. D is catabolized into calcitrioic acid in liver and excreted by the kidney.
A wide range of potential action is postulated by Vit. D upon various dermatological diseases including verrucae, hair disorders, acne, atopic dermatitis, skin cancers, vitiligo, psoriasis, cutaneous tuberculosis, ichthyosis, chronic urticarial, and keloid.
In keloid scars, Vit. D has been shown to prevent tissue fibrosis, inhibiting growth of keloid fibroblasts via preventing TGF -β induced extracellular matrix synthesis and serving as an anti-inflammatory agent.