Sunscreen and Vitamin D. Part II: Sunscreen, SPF and Impact on Vitamin D.

Sunscreens were available in ancient societies, such as Egypt, Greece, Arabia, and Japan, often to help keep the skin lighter and more fashionable. With the promotion of a tan as a sign of a leisurely, privileged lifestyle came the discovery of the harmful effects of sunlight on the skin. These include skin cancer, discovered by Unna and experimentally confirmed by Findlay, which paved the way for sunscreens to be used as protectors rather than just skin lighteners. The sun protection factor was born out of the recognition of the need to assess the ability of sunscreens to protect against skin damage from the sun. Sunscreens are now widely recognized as part of preventive therapy against skin cancer and several photodermatoses. Especially for protection against the former, the UV protection factor has been developed, which can be seen as the equivalent of the sun protection factor for clothing. Data from experimental and observational studies, which are often controversial, suggest that vitamin D levels may decline with increased sun protection, whether from sunscreens or clothing.