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Irritancy test may need modifying for colour ingredients, says European safety committee

By Katie Bird , 23-Dec-2010

An alternative to animal skin irritation tests, Episkin, may need to be modified for testing coloured ingredients, according to a European Safety Committee.

Episkin was validated for use as an alternative to the Draize rabbit skin irritation test in 2007 and the European Scientific Committee on Consumer Safety has since been looking at data submitted by industry regarding its sensitivity to certain substance classes including hair dye ingredients.

The data submitted by industry concerned ingredients such as UV filters, preservatives and skin conditioning agents, as well as a group of hair colouring ingredients.

SCCS said the hair dye ingredients were requested in particular, as there were concerns that coloured ingredients could interfere with the MTT assay testing method. The MTT assay tests for cell proliferation and survival, and uses yellow salts that turn to a purple colour; according to the SCCS, dye ingredients could interfere with the interpretation of the test results.

The SCCS assert, in the opinion published last week, that the data submitted on the 26 hair dye ingredients did not prove that it can be reliably used as an irritation test for such ingredients in its current form.

In the opinion it suggested that different endpoints were used to measure the results that were not reliant on the interpretation of colours, for such ingredients.

High correlation between in vivo and in vitro

However, for the other 15 compounds tested including UV filters, skin conditioning agents and preservatives, the SCCS said there was a relatively high correlation between the in vitro tests and the in vivo controls; although it did note that only 2 of the 3 irritating substances were could be identified by the Episkin method.

Episkin is provided by SkinEthic Laboratories, acquired by L’Oreal in 2006, which also offers the Reconstructed Human Epidermis (RHE) method for skin irritation validated by ECVAM in 2008.

According to the company, RHE can replace the in vivo Draize rabbit skin test the irritation and corrosive potential of cosmetic ingredients and products.

RHE has an overall accuracy of 85 with a false positive rate of 20 and a false negative rate of 10, SkinEthic claims.
With a 42 minute exposure time and a 42 hour incubation time, the model is easy and ready to use, the company said.