A number of in vitro skin irritation tests have been officially validated and are accepted in the OECD guidelines such as OECD439 (OECD, 2013c). The methods are based on reconstructed human epidermis. Taking the EpiSkinTM method as an example, the SCCS expressed concerns over potential interference with colour formation from reducing substances, hair dyes and colourants (SCCP/1145/07)..