## 9 Future Directions and Research
Studying the impact of genetic variations in vitamin D's metabolism on skin health and sensitivity to topical treatments, as well as how factors like skin type, age, and lifestyle affect vitamin D-based cosmetics, will aid in the development of more tailored and customized products, towards several skin conditions [279]. Additionally, during the rise in machine learning, and artificial intelligence (AI)-driven skincare diagnostics, vitamin D products could be tailored to an individual's needs. AI tools are able to analyze genetic markers, skin type, and environmental factors, with a view to recommend personalized vitamin D products, ensuring maximum efficacy for different users [280,281]. Three-dimensional bioprinting could revolutionize personalized vitamin D cosmetic formulations, as custom-printed patches or masks, for instance, can deliver precise, individual-specific dosages [282]. Further clinical evidence is essential to support the benefits of vitamin D in cosmetics/cosmeceuticals. Large-scale, carefully monitored clinical trials should assess the effects of vitamin D on various skin disorders, like eczema, acne, and aging [283]. The widely known vitamin D benefits in promoting cell differentiation and proliferation suggest its potential use in wound-healing and scar management applications. Future cosmeceuticals could incorporate vitamin D for post-surgical or post-operative skincare, burn recovery, and minimizing scar appearance, effectively [25,284,285,286,287]. Moreover, as vitamin D plays a significant role in collagen synthesis and photoaging prevention, further studies could elaborate on its interaction with peptides, growth factors, or retinoids to develop comprehensive anti-aging solutions. Such products may target wrinkles, fine lines, and loss of elasticity, improving overall skin health and barrier function [25,34,63]. Cross-disciplinary research, involving dermatology and endocinology, could offer deeper insights into the systemic and topical effects of vitamin D on skin health. Such an interesting approach may lead to innovations in treating chronic skin conditions, such as psoriasis and atopic dermatitis, while improving general skin vitality and wellness [288,289]. In addition to clinical evaluation, these trials should incorporate patient-reported outcomes and quality of life assessments. Robust clinical data will help advocate for the use of vitamin D in skincare products and guide both consumers and healthcare professionals in making rational decisions. Consumer education is crucial for the successful integration of vitamin D into cosmeceuticals. Prospective investigations ought to concentrate on strategies aiming to augment consumers' comprehension of the benefits and constraints of vitamin D in skincare. This entails developing educational campaigns that define the differences between systemic and topical vitamin D, as well as establishing reasonable performance standards for such products. Educating consumers about proper usage, possible interactions with other products, and the significance of a thorough skincare routine is believed to be a major key in integrating vitamin D in the cosmetic, cosmeceutical, and nutticosmetic field [283]. Furthermore, future vitamin D-based cosmetics can involve the exploration of plant-derived precursors or lab-synthesized alternatives, which could ensure that such products align with vegan, cruelty-free, and environmentally sustainable practices [290,291]. Finally, as vitamin D applications in cosmetics and nutticosmetics expand, global regulatory alignment, ensuring consistent guidelines and transparency in product labeling for its safe and effective use across regions, will be crucial [290,291]. Ultimately, the future of vitamin D in cosmetics or cosmeceuticals holds significant promise, but advancing in this field requires addressing several key research and development areas.