Institut Dr. Schrader Hautphysiologie, Holzminden, Germany.
Curr Probl Dermatol. 2021;55:144-156. doi: 10.1159/000517664. Epub 2021 Oct 25.
BACKGROUND/AIMS: In order to define a label SPF of topically applied sunscreens, in vivo test methods like ISO 24444, FDA Guideline, and the Australian Standard are used worldwide. The basis of all these methods is to induce an erythemal skin reaction by UV irradiation to find the level of MEDu and MEDp (Minimal Erythmal Dose unprotected and protected). In vitro methods replacing the human skin by any kind of nonhuman material are still not available. Thus, offering the new hybrid diffuse reflectance spectroscopy (HDRS) technique that can maintain an in vivo level for SPF testing while neglecting the UV-dose-related erythemal skin reaction is a perfect combination to take care of sun protection and any ethical concerns in SPF testing nowadays.
HDRS is a combination of in vivo diffuse reflectance spectroscopy measurements on the skin and in vitro transmission measurements of a sunscreen on a roughened polymethylmethacrylate plate. By this technique, the in vivo behavior of the investigated sunscreen on the skin is measured as well as the UVB absorption, which is still nonvisible in the reflectance technique. In order to establish an alternative method for in vivo SPF and UVA-PF testing, a huge number of sunscreens (250 samples) were measured by HDRS and compared with the worldwide accepted standards ISO 24444, ISO 24442, and ISO 24443. The variety of sunscreens measured reflect a wide range of different types of formulations as well as a wide range of SPFs (5-120) to validate this new alternative SPF testing procedure.
Far-reaching statistical data analyses show an excellent link between the new nonerythemal-driven HDRS-SPF technique and ISO 24444 results. In the same way, HDRS-UVA-PF results can be correlated with UVA-PF values calculated from ISO 24442 as well as from ISO 24443. The importance of the inclusion of a spectral ratio of photodegradation is shown in the comparison of photostable and photounstable products.
Owing to the elimination of any erythemal-relevant UVB and UVA doses, absolutely no skin reaction occurs during the HDRS experiment. Consequently, there is no need to define an MED anymore. For the first time, an alternative way to arriving at SPF and UVA-PF values is shown, without any ethical concerns of SPF testing in vivo and/or any restriction of SPF testing in vitro. Regardless of the type of formulation or the level of protection, an excellent correlation between SPFHDRSand SPF24444as for sunscreen labeling could be found. By this new alternative nonerythemal technique, not only SPF values can be measured but also UVA-PF values can be calculated with a linear correlation to ISO 24442 as well as to ISO 24443 from the same set of data. By this a robust alternative test method of SPF and UVA-PF values is described, taking into account the interaction of sunscreen formulation and skin.
背景/目的：为了给局部应用防晒霜定义 SPF 标签，目前全球范围内使用 ISO 24444、美国食品药品监督管理局指南和澳大利亚标准等体内测试方法。所有这些方法的基础都是通过紫外线照射诱导红斑皮肤反应，以找到 MEDu 和 MEDp（未保护和保护时的最小红斑剂量）的水平。目前，还没有能够替代人体皮肤的任何非人体材料的体外方法。因此，提供一种新的混合漫反射光谱（HDRS）技术，在进行 SPF 测试时可以保持体内水平，同时忽略与紫外线剂量相关的红斑皮肤反应，这是一种很好的组合，可以兼顾防晒和目前 SPF 测试的任何伦理问题。
HDRS 是在皮肤上进行体内漫反射光谱测量和在粗糙的聚甲基丙烯酸甲酯板上对防晒霜进行体外透射测量的组合。通过该技术，可以测量研究防晒霜在皮肤上的体内行为以及紫外线 B（UVB）吸收情况，而这在反射技术中仍然不可见。为了建立一种替代体内 SPF 和 UVA-PF 测试的方法，对大量防晒霜（250 个样本）进行了 HDRS 测量，并与全球公认的标准 ISO 24444、ISO 24442 和 ISO 24443 进行了比较。所测量的防晒霜种类繁多，反映了各种不同类型的配方以及广泛的 SPF（5-120）范围，以验证这种新的替代 SPF 测试程序。
广泛的统计数据分析表明，新的非红斑驱动 HDRS-SPF 技术与 ISO 24444 结果之间存在极好的联系。同样，HDRS-UVA-PF 结果可以与从 ISO 24442 以及 ISO 24443 计算得出的 UVA-PF 值相关联。在比较光稳定和光不稳定产品时，光降解光谱比的纳入显示了其重要性。
由于消除了任何与红斑相关的 UVB 和 UVA 剂量，在 HDRS 实验过程中皮肤不会产生任何反应。因此，不再需要定义 MED。首次展示了一种替代方法来获得 SPF 和 UVA-PF 值，而无需考虑体内 SPF 测试的任何伦理问题和/或对体外 SPF 测试的任何限制。无论配方类型或保护水平如何，都可以发现 SPFHDRS 和 SPF24444 之间的防晒霜标签极好的相关性。通过这种新的非红斑技术，不仅可以测量 SPF 值，还可以通过与 ISO 24442 以及 ISO 24443 的线性相关关系计算 UVA-PF 值，而这些数据来自同一组数据。通过这种考虑防晒霜配方和皮肤相互作用的稳健替代 SPF 和 UVA-PF 值的测试方法，可以提供更好的防晒效果。
