Sunscreen products: What do they protect us from?

Abstract

Whereas for fifty or so years acquiring a tan has been the trend for aesthetic reasons relating to current beauty criteria, the health authorities are now advocating vigilance in this area, prompted by the knowledge of the harmful effects of the sun, especially from its ultra-violet rays. In the European Union, sunscreen products are considered cosmetics and tests on their effectiveness can be performed in vivo or in vitro to determine four effectiveness indicators: the SPF (Sun Protection Factor), the PF-UVA (UVA Protection Factor), the SPF/PF-UVA ratio and the critical wave length. It is the erythemal SPF which is measured in the vast majority of cases: it can therefore be confirmed that sunscreen products protect us from sunburn under good conditions of use. We thought it would be interesting to calculate other indicators to assess protection against non-melanoma skin cancers (NMSC) and to quantify the effectiveness of the product against UVA1 or UVA2. To characterize the products tested, we have determined in vitro different SPF and PF-UVA values, by using not just the erythemal weighting factor but also the weighting factor relating to the non-melanocytic skin cancer (SPF cnm and PF-UVA cnm), by getting away from any weighting factor (SPF m and PF-UVA m) and lastly, by varying the integration limits to quantify the effectiveness of the tested product in the UVB (290–320 nm), UVA1 (340–400 nm) and UVA2 320–340 nm) fields. In this way, and using these new indicators, we have been able to qualify eleven commercial products—ten cosmetic products and one medical device. It can be interesting to take into account the non-melanocytic skin cancer protection in order to qualify the sunscreen products.