46 ANTI-POLLUTION
matter was employed. Systemic analyses targeted four core mechanisms of action: reducing the initial adhesion of pollutant particles on pretreated skin (anti-adhesion) and enhancing their rinse-off (removability), decreasing the penetration of harmful substances into the skin (anti-penetration), and finally, facilitating the active removal of pollutant particles using cleaning agents (cleansing). The test results were then used to create new and effective formulations for each category.
Anti-adhesion and removability: Keeping particulate matter off the skin Based on the assumption that keeping particulate matter off the skin should be the first line of defence against pollution- induced damage, a new standardised test method was designed to evaluate the effects of typical formulation components – polymers, emollients and emulsifiers – on pollutant adhesion and removability (i.e. rinse-off from pretreated skin). Tests were conducted on the volar
forearm of volunteers. It was gently cleaned with an ethanol-soaked tissue and, after drying, the test sample was applied to the test areas. One area was not treated with a product but was otherwise subjected to the same test procedure and then used as a reference (untreated). Polymers were tested as aqueous solutions with a pH value of 6.5 and 1 percent active matter. Emollients and emulsifiers were tested in simple standardised formulations. After a 10- minute drying time, the model pollutant was applied to the test area via a standardised blast of air. Activated charcoal was used as a model pollutant and was applied via a closed system to ensure inhalation exposure was avoided. Thereafter, 500 ml of lukewarm water was gently and evenly poured over the test site. Photographs of the test areas were taken under controlled light conditions after each step. Image analyses were used to evaluate the amounts of particles adhering to the skin by determining changes to the mean skin lightness. A schematic representation of the procedure used is depicted in Figure 1. The results allowed conclusions to be drawn about a specific ingredient’s ability to decrease particle adhesion and/or improve their removability. As an example of study results, of the
fifteen polymers tested, eleven were able to reduce adhesion compared to untreated, polluted skin, while four of them achieved an opposite effect. Rheocare®
C Plus
obtained the best anti-adhesion results with a reduction of nearly 60 percent achieved (see Fig 2). The performance of polymers also varied in terms of removability. While Tinovis®
GTC UP reduced adhesion slightly less than Rheocare C Plus, it exhibited PERSONAL CARE EUROPE
Apply test product & wait until dry
Apply test pollutant on test areas
Rinse-off
Adhesion
Removability Figure 1: Test method to assess adhesion and removability of particulate matter.
300 250 200 150 100 50 0
-50 -100
Figure 2: Anti-adhesion test using aqueous polymer solutions (1 percent): amount adhering to the skin in relation to untreated skin (baseline = 0); the higher the score, the more PM adheres to the skin.
better removability of the particles. And although Hispagel®
200 significantly
increased adhesion, the removability of particles with this polymer proved to be good (not all data shown). For emollients and emulsifiers, studies
were conducted in a similar manner. Cetiol® Ultimate exhibited low adhesion values similar to that of untreated skin, whereas the other eight emollients studied led to an increase in adhesion. Of twelve emulsifiers tested, the sugar-based emulsifiers Emulgade®
Sucro Plus and Emulgade PL
68/50 performed best, the latter also showing the highest degree of removability with 71 percent. The components that exhibited the best
anti-pollution performance in the first test series were then used to develop three skin care formulations (SC-DE-17-017-48, SC- DE-18-117-2 and SC-DE-17-017-54) with improved anti-pollution effects.6,7,8
The
formulations also contained additional ingredients that addressed other important aspects of skin care products such as skin compatibility, moisturisation or UV protection, as well as ingredients to counteract additional effects induced by
pollutants (e.g. anti-oxidants against oxidative stress or chelators against metals). For formulations claiming “Cosmos” and “vegan” conformity, the natural based polymer Rheocare XGN can be used, as done for SC-DE-18-117-2. Using the same experimental set-up as
before, the test formulations were compared to three benchmark products marketed with anti-pollution claims. Whereas the benchmark products increased adhesion compared to untreated skin and reduced removability, the test formulations exhibited excellent anti-adhesion and rinse-off properties, with virtually no particles detectable on the skin (Fig 3B). In addition, formulation SC-DE-17-017-48 exhibited the tendency to reduce particle adhesion to levels somewhat below those of untreated skin (Fig 3A). The same trends were observed when using particles with a diameter of 2.5 and 80 µm.
Anti-penetration: building a protective film on the skin As demonstrated in the first test series, the adhesion of particulate matter to the skin can be limited when using suitable formulation
November 2020
Pollutant adhesion rel. to untreated skin [%] worse
better
Cosmedia® Cosmedia®
Cosmedia® Cosmedia®
ACE DC
Cosmedia® SP Triple C
Hispagel® Luviflex® Luvigel®
Luvimer®
Ultragel 300 200 Soft EM
Luvigel® Star 100P
Luviquat® Supreme Luviset® Luviset® Luviskol®
Clear One
Plus
Rheocare® C Plus Rheocare®
HSP
Rheocare® XGN Tinocare®
GL Tinovis® GTC UP
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