Sunscreen products: what do they protect us from?

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.

In vitro UV-A protection factor (PF-UVA) of organic and inorganic sunscreens.

The objective of this research was to evaluate the efficacy of various sunscreen agents incorporated into an O/W emulsion. Within the scope of this study only an in vitro method was used. According to selected filter UVA, we can obtain more or less effective creams. With the seven available filters, we can cover a range of values between 2 and 12. In addition to these seven filters absorbing in UVA range, variously coated titanium dioxide and zinc oxide were tested as well. So it appears that the best organic UVA filter is anisotriazine at 10% (PF-UVA = 11.82). Its effectiveness is comparable with that of the titanium dioxide forms used at 25%. Photostability in Suntest showed that the more photostable UVA-filters are the benzophenones.

Effect of the combination of organic and inorganic filters on the Sun Protection Factor (SPF) determined by in vitro method.

This paper describes the effect on Sun Protection Factor (SPF) of the combination of inorganic and organic filters in sunscreen products as determined by an in vitro method. O/W emulsions containing inorganic filters, such as titanium dioxide and zinc oxide, combined with 18 EU-authorized UV-B organic filters were tested. SPF measurements were carried out using a spectrophotometer equipped with an integrating sphere. This study observed a synergic effect when titanium dioxide was combined with either anisotriazine or octyldimethylPABA. The combination of zinc oxide with 11 UV-B organic filters also exhibited a similar synergy; however, the measured SPF was systematically lower than the protection factor achieved with titanium dioxide.