## 7 Vitamin D in Cosmetics and Cosmetics
### Mechanism of Action
\begin{table}
\begin{tabular}{p{71.1 pt} p{71.1 pt} p{71.1 pt} p{71.1 pt} p{71.1 pt}} \hline \hline
**Cosmetic Type** & **Purpose of Vitamin D** & **Effects** & **Examples** & **References** \\ \hline Acne treatments & Reduces inflammation and promotes healing & Reduce skin sebum, clear acne scars & Acne serums with vitamin D & [225] \\ \hline Psoriasis treatments & Reduces inflammation & Help keratinocyte regeneration & Ointments & [219; 226; 227; 228] \\ \hline Cleaners & Mild exfoliation and hydration & Cleanse without stripping natural oils & Cleaners with vitamin D derivatives & [121] \\ \hline Scalp treatments & Improves scalp health and prevents dandruff & Reduce flakiness, support hair follicle health & Shampoos, hair oils, and scalp serums & [210] \\ \hline Hand creams & Repairs cracked skin, enhances hydration & Improve moisture retention and south dry skin & Hand creams with vitamin D & [229] \\ \hline \hline \end{tabular}
\end{table} 
Table 4: \(Cont.\)The anti-inflammatory properties of vitamin D play a critical role in its skin activity [27; 37; 230]. By upregulating anti-inflammatory cytokines and downregulating pro-inflammatory ones, vitamin D highly participates in the immune response. This skin-correlated activity is especially helpful in the treatment of inflammatory skin diseases like psoriasis, since it reportedly reduces inflammation and excessive skin cell turnover, mainly by inhibiting T cell proliferation and further regulating the formation and repair of skin cells [37]. Through the facilitation of cellular processes involved in tissue repair and regeneration, it aids in the healing of wounds. Topical vitamin D application also promotes keratinocyte migration and proliferation to the wound site, hastening the closure of wounds and aiding in the repair of injured skin [37]. Vitamin D provides, additionally, defense against UV-induced oxidative stress, due to its antioxidant qualities of effectively neutralizing free radicals, and thus, aids in the prevention of skin damage and premature aging and the promotion of the overall skin resilience and health [37]. Skin health is significantly impacted by vitamin D, and its therapeutic advantages are mediated through several pathways [25]. By maintaining the epidermal barrier and facilitating the development of epidermal keratinocytes, vitamin D encourages the skin to function as a protective barrier, less vulnerable to infection and environmental harm, towards a potential injury and keratinocytes maturing properly [25; 27]. Furthermore, this hormone plays a critical role in controlling the proliferation of cells in the epidermis, as it regulates aberrant cell growth, which is important in conditions like psoriasis with increased rates of cell turnover [25]. Finally, vitamin D helps to promote skin health during the skin renewal process, relieves the symptoms of skin-associated comorbidities, normalizes epidermal growth, and enhances cell proliferation as well as repair activities, functions that make this hormone a useful tool in the treatment of wounds and skin injuries, since it primarily speeds up the healing process of injured skin [25].