DermaTronnier, Institute for Experimental Dermatology at the Witten/Herdecke University, Witten, Germany.
UV-Technik, Hanau, Germany.
Skin Pharmacol Physiol. 2020;33(2):77-85. doi: 10.1159/000505218. Epub 2020 Jan 24.
Sunscreen products aim to help protect the skin against UV radiation and consequently reduce the risk of early skin ageing and skin cancer. However, it is well known that some sunscreen ingredients are not photostable, but this usually refers to irradiation with UV light. Moreover, it has to be mentioned that a relative cumulative erythema effectiveness compliant light source is used for the in vivo sun protection factor (SPF) testing. Here, UV simulators equipped with a xenon arc lamp use filters such as WG320 and UG11 (thickness 1 mm) to minimize infrared (IR) radiation and wavelength below 300 nm. However, under practical conditions, the sunscreen product is not only exposed to UVA/B light, but also to visible light (VIS) and IR light. In fact, the spectrum of solar radiation is composed of approximately 7% UV, 39% VIS and 54% IR.
To investigate the influence of short-wave and long-wave radiation on the photostability of sunscreens.
Irradiation was performed with the Suntest CPS+ that is considered to closely imitate solar radiation. The filter UG11 (thickness 1 mm), which absorbs much of the VIS and IR light, and the glass filter WG320 (thickness 2 mm), which effectively absorbs radiation of wavelengths less than 300 nm, were used in the Suntest CPS+ both individually and in combination and were inserted between the light source and the samples. The following transmission measurements were carried out with Labsphere's UV-2000s device. Here, the effectiveness (percentage change of SPF before irradiation to SPF after irradiation) as a measure of the photostability was calculated.
As expected after total solar spectrum irradiation, the effectiveness in all tested sunscreens is lower compared to relative cumulative erythema effectiveness light used for in vitro testing of SPF. In the reference sunscreen formula S2 as well as in the two different sunscreen products, especially long-wave radiation (>400 nm) had an effect on photostability, whereas short-wave radiation had only a minor impact. In contrast, in the BASF sun care gel line only short-wave radiation below 300 nm had an effect on photostability, and blocking VIS and IR light had no effect at all.
Based on these data, we can conclude that short waves and/or VIS + IR light have an influence on the photostability of sunscreens.
防晒霜旨在帮助保护皮肤免受紫外线辐射，从而降低皮肤过早老化和皮肤癌的风险。然而，众所周知，一些防晒霜成分不是光稳定的，但这通常是指紫外线照射。此外，必须提到的是，相对累积红斑效应合规光源用于体内防晒因子 (SPF) 测试。在这里，配备氙弧灯的紫外线模拟器使用 WG320 和 UG11（1 毫米厚）等过滤器来最小化红外线 (IR) 辐射和波长低于 300nm。然而，在实际条件下，防晒霜不仅会受到 UVA/B 光的照射，还会受到可见光 (VIS) 和 IR 光的照射。事实上，太阳辐射的光谱由大约 7%的 UV、39%的 VIS 和 54%的 IR 组成。
研究短波和长波辐射对防晒霜光稳定性的影响。
使用被认为能更接近模拟太阳辐射的 Suntest CPS+进行照射。使用 UG11（1 毫米厚）过滤器，它吸收了大部分 VIS 和 IR 光，以及 WG320 玻璃过滤器（2 毫米厚），它能有效吸收波长小于 300nm 的辐射，在 Suntest CPS+中单独使用和组合使用，并插入光源和样品之间。使用 Labsphere 的 UV-2000s 设备进行以下透射测量。在这里，作为光稳定性的衡量标准，计算了有效性（照射前的 SPF 与照射后的 SPF 的百分比变化）。
正如在全太阳光谱照射后所预期的那样，与用于体外 SPF 测试的相对累积红斑效应光相比，所有测试防晒霜的有效性都较低。在参考防晒霜配方 S2 以及两种不同的防晒霜中，特别是长波辐射（>400nm）对光稳定性有影响，而短波辐射只有很小的影响。相比之下，在 BASF 护肤凝胶系列中，只有低于 300nm 的短波辐射对光稳定性有影响，而阻挡 VIS 和 IR 光则完全没有影响。
基于这些数据，我们可以得出结论，短波和/或 VIS+IR 光会影响防晒霜的光稳定性。
