The present Test Guideline addresses the human health hazard endpoint skin sensitisation, following exposure to a test chemical. Skin sensitisation refers to an allergic response following skin contact with the tested chemical, as defined by the United Nations Globally Harmonized System of Classification and Labelling of Chemicals (UN GHS).

This Test Guideline provides an in chemico procedure (Direct Peptide Reactivity Assay – DPRA) used for supporting the discrimination between skin sensitisers and non-sensitisers in accordance with the UN GHS.

The DPRA is proposed to address the molecular initiating event leading to the skin sensitisation, namely protein reactivity, by quantifying the reactivity of test chemicals towards model synthetic peptides containing either lysine or cysteine. Cysteine and lysine percent peptide depletion values are then calculated and used in a prediction model to categorise a substance in one of four classes of reactivity for supporting the discrimination between skin sensitisers and non-sensitisers.