108 TESTING
concerns related to animal and human welfare but also provides data that is directly applicable to human eye health.12,13 The OECD TG 492 test works by applying a
substance to the RhCE model and assessing its effect on vitality of the respective tissue. If the product does not result in a reduction of vitality below a certain limit, it is deemed non-irritative for eyes.
This approach generally provides
useful information for regulatory agencies to figure out if a product that would theoretically be subject to mandatory hazard labeling because of its ingredients can omit the hazard symbol. Like the BCOP test and the HET- CAM test, the OECD TG 492 is, therefore, focused on identifying substances that do not cause eye irritation or serious eye damage (GHS category ‘non-irritant’).14 In general, OECD tests are internationally
24 % ics
recognised standards that have been developed for the evaluation of substances and products in areas such as chemistry, the environment and health. Many OECD test methods promote alternative approaches, such as in vitro testing or computer-based models, to minimise animal testing. Regulatory compliance ensures that companies’ products meet legal requirements, e.g. in the EU or in other markets that recognise OECD standards. Due to its many advantages, Dermatest offers the OECD TG 492 for many years. However, even the OECD TG 492 comes with
certain limitations. OECD TG 492 is suitable for distinguishing severe to moderate irritation from mild irritation, but is not reliably suitable for distinguishing between mild and very mild irritation. However, this is precisely the area that is often of interest, particularly for cosmetics. To better assess the need for a more tailored
reliable test design to identify mild and very mild products, we evaluated which categories
18%
■ Cosmetics ■ Raw material/Chemical
■ Detergents/Home care products
the appropriate test. Raw materials and home care products can be tested for their irritant potential to rule out damage to the eye. In this way, the suitability of the chemicals as additives can be scientifically proven. Evidence can also be provided as to whether a warning label is necessary on a home care product that could accidentally get into the eye, or whether it can be dispensed with. However, the question for cosmetics
58 %
can only be partially answered by OECD TG 492, although it is one of the best variants of the common in vitro methods on the market. In case of cosmetic products containing surfactants, such as shampoos, OECD TG 492 can only provide a rough classification of the irritation
potential. That means OECD TG 492 can be used
Figure 1: Percentage distribution of performed OECD TG 492 tests according to the respective product category of the product tested
Raw material / Chemicals
products that had already been tested by OECD TG 492 belonged to. A database analysis was carried out for this purpose. Basically, the products that have been tested can be divided into three categories: raw materials/chemicals, home care products/detergents and cosmetics. Across all categories the actual products
span from industrial cleaners, such as drain cleaners, to personal care items like shampoos and eye makeup. Nevertheless, cosmetics constitute the majority of tested products (58 %). 18% of all tested products were raw materials/chemicals and 24 % were home care products/detergents. For a large proportion of the products
analysed, testing according to OECD TG 492 is Detergents / Home care p
to separate shampoos with a high irritation potential from those with a lower irritation potential. A further, more nuanced classification is not possible, especially in the mild to extra mild range. Therefore, only looking at the OECD TG 492 results deprives cosmetic manufacturers of the opportunity to find out, for example, which of their formulations is best suited for sensitive eyes.
This limitation of OECD TG 492 becomes
even clearer for products where no irritating characteristics are assumed anyway like e.g. for eye cremes or serums. In these cases the resolution of OECD TG 492 is often not even sufficient for a rough classification of the irritation potential. Thus, when only tested according to OECD
TG 492, the majority of those products, would simply be classified as non-irritating, meaning that particularly mild products could not be identified further because the testing protocol and prediction model of OECD TG 492 is not designed for these cases. Nevertheless, the labelling of products
that are mild or very mild is of great benefit to sensitive end user groups, such as children or end-users with sensitive eyes, so identifying these products is particularly important.
Dermatest’s ‘No Tears’ test design To address the growing demand for safe and gentle cosmetic products, Dermatest has established the ‘No Tears’ test design, an advanced in vitro testing approach specifically focused on identifying mild to extra-mild cosmetic products. This method utilizes the same reconstructed human cornea-like epithelium (RhCE) models as the OECD TG 492 test, but with modified exposure scenarios tailored to better represent the range of mild and very mild products. Thus, the ‘No Tears’ test is designed to offer a
more precise assessment of a product’s potential for irritation, particularly for products intended for sensitive areas, such as the eyes. The central idea behind the ‘No Tears’ test is to observe and evaluate how a cosmetic product interacts with the RhCE models over a period of time. The key metric in this process is the time it
Figure 2: Example of MTT assay. A strong colour development is to be equated with high vitality. From top to bottom: Row 1 adult shampoo, row 2 children’s shampoo, row 3 baby shampoo, row 4 negative and positive control; samples after different time points
PERSONAL CARE April 2025
takes for the product to reduce the viability of these tissues by 50%. This measurement, known as the Effective Time 50 (ET-50) value, provides
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