TESTING 57
Taking the sting out of mildness testing
Carol Treasure – XCellR8, UK Stewart Long – Cutest, UK
To address the first question of why we need to have a new method to predict skin mildness it is important to realise there is clearly an increasing demand from consumers for milder and milder products. In line with that, companies are finding that there is an increasing demand to substantiate marketing claims that are going to differentiate them from the rest of the market. In addition, existing animal data is used to validate in vitro methods on a regular basis. That is the gold standard. What we wanted to do instead was to move away from that quite archaic approach and to make sure that we could validate our in vitro methods against real human data which is much more scientifically relevant to the cosmetics of today. XCellR8 embarked on a research project together with Cutest with funding from
ET50
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1 10 Time (h) ET50
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1 10 Time (h) Figure 1: In vitro irritation potential of 4 surfactants. February 2020 PERSONAL CARE EUROPE 100
determination of B 0.3% CAPB
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1 10 Time (h) 100
determination of A 0.3% SLES
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1 Time (h) ET50
determination of D 0.3% Biosurfactant
Rank order of irritancy using linear extrapolation and logic equation
ET50 9.37
C > A > 10.25
B 29.4 D 38.08 100 Abstract
Why does the industry need a new model to predict mildness to skin? In this article we will cover what the existing methods are and what their limitations might be, and also how we worked on those and optimised those to create a new model. The correlation between in vitro testing for skin irritation and in vivo testing for skin irritation. At the end of the article we will also offer some real world applications.
Innovate UK. The aims of the work were to firstly optimise in vitro and in vivo test methods, to make sure that they were sensitive enough to detect very subtle differences between mild formulations, and then to assess the predictive capacity of those tests.
Existing methods
It is important to think about the existing methods for skin irritation testing and in
ET50
determination of C 0.3% SLS
vitro, this currently happens at a regulatory level around the world using three- dimensional skin models. Ingredients in products are applied directly to the tissue surface so it provides a good model of what happens in real life exposure to cosmetics. But one of the drawbacks is that the
standard OECD test guideline only measures a single exposure time and it gives a straightforward “yes” or “no” answer, whether the ingredient or
A SLES B CAPB C SLS
D Biosurfactant
Test items (0.3%, pH 4.7) at 1, 5, 18, 24, 48hrs
Percentage of viability relative to untreated control
Percentage of viability relative to untreated control
Percentage of viability relative to untreated control
Percentage of viability relative to untreated control
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