34 TESTING
This product is 8 times more expensive than its neighbour, but is equally ultra-mild
These 2 products are from the same brand but the soap is notably milder
Products above this line are classed as non-irritant - the mildest classification available
This media favourite claims its low pH levels make it milder than other soaps
Figure 7: The relative ET50 values of various soaps (pink) and face cleansers (grey). Using the XtraMild method, the ET50 values of newly tested products can be compared with a historic database of results
Ab initio test development An example of a test developed to be animal- product-free from the outset is XCellR8’s method for predicting skin mildness, XtraMild. Demand is increasing from consumers for ever milder products, allowing them to feel confident even when their skin is particularly sensitive.
This, in turn, increases demand
on formulators & marketing teams for differentiating claims. The XtraMild test was developed over a two-year research project funded by Innovate UK, with the aims of optimising an in vitro test for maximum predictive sensitivity and be able to differentiate between the very mildest products and formulations. Given that animal-derived products
would not be considered as part of the test, a suitable test system had to be selected. Reconstructed human epidermis - a 3D human skin tissue model - is widely used in safety assessment and is suitable for testing both ingredients and finished products. Though not the same thickness as human
skin, they contain the representative layers identified in human skin, and allow direct application of the test item to the tissue surface, making them an excellent model for ‘real life’ exposure. No animal-derived components are required for the maintenance of the tissue model, nor the analysis. Depending on the choice of commercial skin model, this type of test meets Level 5 – Level 7 on our animal product free scale (Figure 2). The standard regulatory test using these tissue models (OECD TG 439) measures a single exposure time to classify irritants versus non-irritants for purposes of hazard identification and labelling. This test was
PERSONAL CARE June 2022
validated against historical animal data (the Draize test). For mild cosmetic ingredients and
formulations, a more sensitive approach is required, capable of not only detecting products that are not irritant in a binary fashion - yes or no - but ranking the potency of the very mildest products. Several other tests using these tissue
model exist which provide an ET50 value, the time taken to reduce the tissue to 50% viability. Although these methods allow determination of a rank order of irritation potential, and comparisons between products, they fail to distinguish differences between the very mildest products. To optimise a test method specifically
for mildness, the timepoints in the existing ET50 methods were extended, observing the effects of a test item for up to 48 hours rather than the previous 18 hours. ET50 values were then determined for a
range of surfactants with a range of irritation potentials and compared against results of human patch testing to develop a prediction model for ultra-mild products. Once again during this process, no reagents of animal- derived origin were used. An extensive process of testing then took
place, analysing various formulations from across several product ranges, including cleansers, face and body washes, soaps, and baby shampoos. This allowed the creation of a database of industry-leading ingredients and formulations to be used as benchmarks in future tests. Any ET50 value generated form the
XtraMild method can now be ranked against similar products which have already been tested, allowing not only a classification of
irritation, but a differentiation between the very mildest products. We are continually growing the database, allowing comparisons.and predictions of skin mildness without the use of animals, or animal-derived products.
The transition to 100% animal-free testing It is clear that work still must be done on the journey to completely remove the use of animals from safety and efficacy testing across a number of industries, with the use of animal components raising both scientific and ethical concerns. Despite this, significant improvements have been made already. Adaptation of regulatory safety tests is
possible but requires significant investment to achieve. The technologies to develop animal- product-free test methods has been developed and will benefit from being made widely available and establishing itself as a topic for education across industry and academia. In vitro testing provides robust safety
information, and is capable of novel innovations for claims, such as the development of databases for benchmarking ingredients and formulations. As consumers become more educated and invested in brands and products, the discussion is likely to move from how is how is something not tested - i.e. avoiding animal tests - to how is something tested. A vegan product already requires a vegan
ingredient list and may well soon require a vegan testing programme also. This offers a chance to present a positive message, of advanced scientific techniques being used to ensure the safety and efficacy of formulations, while remaining animal- product-free.
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ET50 value
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