Department of Chemistry, Technical University of Denmark, Kgs. Lyngby, Denmark.
Riemann A/S, Hillerød, Denmark.
Skin Res Technol. 2022 Mar;28(2):225-235. doi: 10.1111/srt.13115. Epub 2021 Nov 9.
While sunbathing of performing outdoor sport activities, sunscreens are important for protection of uncovered skin against ultraviolet (UV) radiation. However, perspiration negatively affects the performance of a sunscreen film by weakening its substantivity and uniformity through the activation of two mechanisms, namely sunscreen wash-off and sunscreen redistribution.
We used a perspiring skin simulator to investigate the effect of sunscreen formulation on its efficiency upon sweating. Specifically, we modified the sunscreen formulation by incorporating a hydrophobic film former and adding water-absorbing particles. Sunscreen performance before and after perspiration is assessed by in vitro sun protection factor measurements, direct detection of changes in the sunscreen distribution using UV reflectance imaging, and by coherent anti-Stokes Raman scattering (CARS) microscopy for microscopic characterization of the UV filter relocation.
The results show that incorporating a hydrophobic film former can decrease sunscreen wash-off due to sweating, while an excessive amount of film former might negatively affect the sunscreen distribution. The addition of water-absorbing particles, on the other hand, had either a negative or positive impact on the sunscreen substantivity, depending on the particle properties. While the addition of large water-absorbing particles appeared to increase sunscreen redistribution, smaller particles that could form a gel-like structure upon contact with water, appeared to change sunscreen wetting and sweat droplet spreading, thereby decreasing sunscreen wash-off and sunscreen redistribution.
We find that using a combination of hydrophobic film formers, which increase water resistance, and small water-absorbing particles, which change the wetting behavior, can make sunscreen formulations more sweat-resistant and less runny.
在进行日光浴或户外体育活动时，防晒霜对于保护未被覆盖的皮肤免受紫外线（UV）辐射至关重要。然而，汗水会通过两种机制削弱防晒霜膜的持久性和均匀性，从而对其性能产生负面影响，这两种机制分别是防晒霜的洗去和重新分布。
我们使用出汗皮肤模拟器研究了防晒霜配方对其在出汗时效率的影响。具体来说，我们通过加入疏水性成膜剂和添加吸水性颗粒来改进防晒霜配方。通过体外防晒系数测量、使用紫外反射成像直接检测防晒霜分布的变化以及相干反斯托克斯拉曼散射（CARS）显微镜对 UV 滤光片重新定位的微观特征进行评估，来评估防晒霜在出汗前后的性能。
结果表明，加入疏水性成膜剂可以减少因出汗导致的防晒霜洗去，而过量的成膜剂可能会对防晒霜的分布产生负面影响。另一方面，吸水性颗粒的添加对防晒霜的持久性有积极或消极的影响，这取决于颗粒的特性。虽然添加大的吸水性颗粒似乎会增加防晒霜的重新分布，但接触水后会形成凝胶状结构的较小颗粒似乎会改变防晒霜的润湿和汗滴扩散，从而减少防晒霜的洗去和重新分布。
我们发现，使用增加耐水性的疏水性成膜剂和改变润湿行为的小吸水性颗粒的组合，可以使防晒霜配方更耐汗且不易流淌。
