L'Oréal Research and Innovation, 9 Rue Pierre Dreyfus 92110, Clichy, France.
Int J Cosmet Sci. 2019 Oct;41(5):437-442. doi: 10.1111/ics.12556. Epub 2019 Sep 4.
To explore the relationship between skin surface hydration and Trans-Epidermal Water Loss (TEWL) when simultaneously measured.
Six circular skin areas of the forearms (3 per forearm, 3 cm in diameter) of 12 Caucasian women were used as models. 4 prototypes of formulae of different compositions containing glycerol at different concentrations 7%, 10% and 40% were used as models of hydrating products. One formula (glycerol-free) was used as control vehicle. Standardized applications of formulae (2 mg/cm ) were performed on 5 skin sites chosen at random, the other being left as bare/control. A recently marketed instrumental device that records the skin surface hydration and TEWL on a small skin area in a simultaneous manner was used. Measurements were carried out at T0 (pre-application), at 1 h (T1) and 5 h (T5) post applications on two close sites within the 6 defined areas of both forearms.
The new instrumental device allowed to clearly differentiate the 5 formulae (i.e. 7% vs. 10%) with regard the dose effect brought by glycerol (7%, 10%, 40%) and to record their lingering effects at T1 and T5. Both parameters were found significantly and negatively correlated, i.e. the higher the skin hydration, the lower the TEWL. The 40% concentration of glycerol, that leads to the highest skin hydration, brings a drop in the TEWL by about a two-fold factor. Skin hydration of bare skin and control/vehicle sites showed minor and non-significant changes along 5 h. Instead, the control/ vehicle slowed down the TEWL to a slight extent.
The use of this new instrumental device shed a new light on the mutual and inverse relationships between skin hydration and TEWL. Results suggest that, at high concentration, glycerol leads to largely increase the water content of both epidermal and dermal compartments, possibly leading to structural changes in the skin relief.
探索同时测量皮肤表面水分和经皮水分丢失（TEWL）之间的关系。
使用 12 名白种女性前臂的 6 个圆形皮肤区域（每个前臂 3 个，直径 3 厘米）作为模型。使用 4 种不同组成的配方原型，其中含有不同浓度的甘油 7%、10%和 40%，作为保湿产品的模型。一种配方（无甘油）用作对照载体。在随机选择的 5 个皮肤部位标准化应用配方（2mg/cm ），另一个部位留作空白/对照。使用一种新的市售仪器，可同时记录小面积皮肤的皮肤表面水分和 TEWL。在两个前臂的 6 个定义区域内的两个相邻部位，在 T0（应用前）、T1（应用后 1 小时）和 T5（应用后 5 小时）进行测量。
新仪器能够清楚地区分 5 种配方（即 7%对比 10%），甘油（7%、10%、40%）带来的剂量效应，并记录它们在 T1 和 T5 的持续效果。两个参数都显著且呈负相关，即皮肤水分越高，TEWL 越低。40%浓度的甘油可使皮肤水分达到最高，TEWL 下降约两倍。裸皮和对照/载体部位的皮肤水分在 5 小时内变化较小且无统计学意义。相反，对照/载体在一定程度上减缓了 TEWL。
该新仪器的使用为皮肤水分和 TEWL 之间的相互和反向关系提供了新的视角。结果表明，在高浓度下，甘油会使表皮和真皮水分含量大大增加，可能导致皮肤表面结构发生变化。
