Layer Thickness of SPF 30 Sunscreen and Formation of Pre-vitamin D

Abstract

Background: Most studies have demonstrated that sunscreens with lower sun protection factor (SPF) do not prevent the production of vitamin D because much lower amount of sunscreen (SPF<30) is applied than recommended (2 mg/cm²) indicating that a significant amount of UV radiation can penetrate the skin. Since less sunscreen is applied, higher SPF sunscreens may be used to achieve the desired protection. However, there is little information regarding the application of high-SPF sunscreen and vitamin D formation. The aim of this study was to measure the influence of the amount of two SPF 30 sunscreens on pre-vitamin D formation in a cuvette with 7-dehydrocholesterol. Results: Sunscreen with physical (reflecting) or chemical (absorbing) UV filters exhibits different levels of protection in vitro even if the SPF is the same. The level of photoprotection is differentially reduced when less sunscreen than the recommended application thickness is applied. Conclusion: The usual application of 0.8-1 mg/cm² is below the recommended value of 2 mg/cm², and pre-vitamin D may be formed when lower amounts of SPF ≤30 sunscreen are applied, showing that a significant amount of UV radiation may enter the skin.