Abstract

Vitamin D has many benefits for body and human health. Vitamin D is involved in calcium homeostasis and bone metabolism, and it can be obtained from food, but it is produced by the human body too. Vitamin D from foodstuffs is available in two forms; vitamin D2 [ergocalciferol,] is contained in plants, and vitamin D3 [cholecalciferol] is contained in animals. Furthermore, the vitamin D produced by human body, is synthesized mainly in the skin. The synthesis of vitamin D in the skin starts with the conversion of 7-dehydrocholesterol [provitamin D3] to previtamin D by UVB. Some of the formed vitamin D3 in the skin is transported to the liver and metabolized to become 25(OH)D3 (calcidiol), then furtherly converted in two steps to 1,25(OH)2D3 (calcitriol), i.e., the biologically active form of vitamin D. Being produced by the organism, vitamin D shows a high tolerability; thus hypersensitivity reactions to vitamin D are rarely reported in the literature. From vitamin D, many analogs have been used successfully to treat secondary hyperparathyroidism or other derivatives synthetically produced like calcipotriol, calcitriol and maxcalcitol that are used in dermatologic field as topical therapeutic agents for psoriasis. For this last class of compounds, given the external use on the skin, cases of allergic contact dermatitis are described.