Sun protection factors: world wide confusion

Abstract

The Sun Protection Factor (SPF) is a very popular instrument in the marketing of sunscreens. Unfortunately it is often not understood how sunscreens work and where the limitations of the SPF are. A lot of aspects of the SPF are confusing, e.g. the race for higher and higher numbers, the effect on SPF when less sunscreen is applied and if sunscreen should be used at all because they may block the Vitamin D synthesis. All this has a negative impact on compliance by the consumer or patient which is the most important influence factor in sun protection. This paper explains how sunscreens work, how the SPF is determined and where the limitations of the current methods exist. The dynamic view of 'UV radiation applied' and the 'UV dose transmitted' through the sunscreen onto the skin as well as onto a substrate in vitro help in the understanding and are also promising approaches in the in vitro assessment. A variation of the in vitro assessment of a sunscreen is the in silico calculation based on the absorption spectrum of the UV filters and an assumption about the irregular sunscreen film on the skin. The sunscreen simulator program can be used to determine how the SPF is affected by applying smaller amounts of sunscreen. Besides the SPF, UVA protection is also discussed. The degree of UVA protection determines the quality of the overall UV protection, whereas the SPF is an indication of the quantity of protection. Furthermore other protection factors such as IPF, iSPF, RSF and p53, and the inhibition of the Vitamin D3 synthesis by sunscreens are also discussed. In conclusion it is shown that the accuracy and robustness of the SPF and other Protection Factors will improve significantly with the availability of true broad-spectrum sunscreens rather than conventional UVB-biased sunscreens, because uniform protection profiles lead to protection independent of the action spectrum of the endpoint and the UV-radiation source.

Fator de proteção solar: significado e controvérsias

“…Recent publications. 46.47 reinforce the need Thus, as stated earlier, the SPF value should no longer be considered in absolute terms, such as additional exposure time before the formation of erythema.…”

“…Osterwalder and Herzog, 46 in a recent article published, show that the proposed mathematical reasoning could be done in reverse, by analyzing how much energy passes through the sunscreen (transmittance) instead of how much energy is absorbed by it (absorbance) where: T = 1 -A By applying this reasoning, we find that the amount of energy that passes through the sunscreen with SPF 60 (and therefore, affects the skin) would be half of that transmitted by a sunscreen with SPF 30. Thus, the protection offered by the product with SPF 60 would be double that offered by the product with SPF 30, as seen in graph 2.…”

The Children and Sunscreen Study

“…Children applied less than onequarter (median thickness, 0.48 mg/cm 2 ) of the quantity of sunscreen used during SPF testing. Because of the quasilinear relationship between sunscreen thickness and the SPF, 28 these results suggest that children's in-use SPF may be less than one-fourth of the manufacturer's SPF. Sunscreen is often the only form of sun protection used by children 11 ; therefore, they may be less well protected from the sun than parents might expect.…”

“…[16][17][18][19][20][21][22][23][24][25][26][27] Because there is a linear relationship between the thickness of application and the SPF, this may result in a substantially lower SPF than that stated on the bottle. 28 Results of previous studies suggest that sunscreen application thickness may differ when using sunscreen for recreational use 18,19,22 or for daily use 16 and that the type and size of the sunscreen dispenser may influence the amount of sunscreen used. 29 For example, in one study 29 participants used 24 g per application on average when using a large open-mouthed jar but only 10 g when using a tube with a narrow opening.…”

Sekundärprävention von Hauttumoren nach Organtransplantation

“…Hier ist zu beachten, dass der Lichtschutzfaktor bei einer Menge von 2 mg/cm 2 Körperoberfläche bestimmt wird und mit geringerer Menge logarithmisch abnimmt. Wird nur ein Viertel der empfohlenen Menge aufgetragen, beträgt der Schutzfaktor lediglich 3-4 [2,3]. Oft werden Sonnenschutzpraktiken nicht optimal durchgeführt.…”