An in vitro study of the eye irritation potential of new shampoo formulations

Several in vitro methods have been used to investigate the toxicity of potential eye irritants with a view to replacing in vivo eye irritation testing. Initially, a group of surfactant and surfactant-based products, for which in-house in vivo Draize eye irritation data were already available, were studied in a range of in vitro assays. This approach obviated the need to generate in vivo data specifically to evaluate the current in vitro programme. Chinese hamster V79 cells, mouse peritoneal macrophages, mouse Balb/c 3T3 cells and mouse L929 fibroblasts were used together with several different endpoints of toxicity, including dye retention techniques, reductive capacity and morphological assessment. In addition, the samples were tested in a bacterial bioluminescence system, Microtox. The data from previous studies indicated that the best agreement with irritancy data was obtained using a test battery consisting of fluorescein diacetate incorporation by V79 cells, neutral red uptake by 3T3 cells, the L929 agarose overlay assay and the Microtox assay. This report presents an example of the use of this in vitro evaluation process for surfactant-based personal products. In each case, the in vitro toxicity of the new formulation was compared with that of a range of related products for which historical eye irritation data, generated using either the Draize test in vivo or the enucleated eye assay in vitro, were available. The data for each in vitro assay were evaluated by comparing the toxicity rank order with the available historical data. In general, the in vitro ranking was in good agreement with the historical data, although the L929 assay proved to be of limited value. This approach allowed the completion of the safety evaluation process for the novel formulations.