48 ANTI-POLLUTION
was developed that allowed quantification of the cleansing performance of ingredients and formulations on polluted skin. Following a small-scale study on human
volunteers, an in vitro test method was developed. The sebum pollution model (SPM) used was based on published literature11
and contained both artificial
sebum, and carbon black with a mean particle size of 0.04 µm and iron oxide with a mean particle size of 1.42 µm as model pollutants. A collagen matrix was used as model skin. The SPM was applied to the collagen matrix, evenly distributed with a soft brush and left to dry before initial pictures were taken. Afterwards, the polluted sample underwent a standardised and automated cleansing process with a cotton pad soaked with either the test product or water (untreated control). Pictures were taken anew, and the colour values extracted to calculate both the cleansing efficacy as well as the potential smearing of the pollutant. Cleansing was defined as the removal of both artificial sebum and model pollutants from the applied area, whereas smearing was considered to be the particles distributed over the test area outside of the application site during the cleansing process. The analysis of eleven emollients revealed
that the cleansing performance is directly correlated to the physicochemical parameters: The best results were achieved with emollients possessing a high spreading value. Six emollients exhibited a cleansing efficacy of around 90 percent or better, while Cetiol Ultimate removed as much as 97 percent of the model pollutant. The samples only treated with water showed the highest amount of remaining SPM (Fig 7A). Similar results were obtained in terms of smearing. Again, Cetiol Ultimate performed best, distributing less than 4 percent of the pollutant over the measured area. Treatment with water only led to extensive smearing of particles over the measured area, reaching a total value of 90 percent (Fig 7B). The obtained in vitro results were
validated by in vivo testing and showed a
120 100 80 60 40 20 0
a
b
Figure 4: Anti-penetration test: (A) schematic representation of the skin and how a topically applied product can lower the absorption of damaging substances; (B) visualization of the penetration of fluorescent dye under test conditions.
high level of correlation: Data collected on cleansing performance displayed a coefficient of determination (R²) of 0.95, those for smearing correlated with a value of 0.89. Based on the emollient screening, the formulation SC-DE-19-077-1312
was
designed. It contains Phytosoothe™ LS 9766 as a bioactive ingredient that helps accelerate skin repair after damage and also has a soothing effect. Compared to benchmark products, the formulation exhibited a very good cleansing performance: It effectively removed more than 85% percent of the sebum pollution
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Reference
Figure 5: Anti-penetration effect of polymers tested in aqueous solutions with 0.125 percent active matter, relative to untreated control (100 percent penetration). The higher the score, the more model pollutant penetrated.
PERSONAL CARE EUROPE Benchmark SC-DE-19-087-11
Figure 6: Anti-penetration performance of the formulation SC-DE-19-087-11 compared to benchmark product, relative to untreated control (100 percent penetration).
November 2020
model in leave-on cleansing tests where the formulation was applied on cosmetic cotton pads. A similar cleansing result was achieved in rinse-off cleansing tests, whereby the formulation was distributed in five cycles using silicone rubber in a standardised manner (Fig 8). While the cleansing efficacy certainly was the focus, other skin care benefits, the sensory profile as well as the consumer experience when applying the formulation were also taken into account. The sensorial profile indicated a high degree of acceptance by the volunteers. In addition, the formulation can either be used as a leave-on cleansing
Penetration [%] better worse
Penetration [%] better worse
Reference Cosmedia® ACE Cosmedia® SP
Cosmedia® Triple C Cosmedia®
Ultragel 300 Hispagel®
200 Luviflex® Soft Luvigel® Star Luviquat®
Supreme Luviset®
One Rheocare® C Plus Rheocare® HSP
Rheocare® XGN Rheocare®
GTC UP
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