This Test Guideline describes an in vitro procedure that may be used for the hazard
identification of irritant chemicals (substances and mixtures) in accordance with
the UN Globally Harmonized System of Classification and Labelling (GHS) Category 2.
It is based on reconstructed human epidermis (RhE), which in its overall design closely
mimics the biochemical and physiological properties of the upper parts of the human
skin. Cell viability is measured by enzymatic conversion of the vital dye MTT into
a blue formazan salt that is quantitatively measured after extraction from tissues.
Irritant test substances are identified by their ability to decrease cell viability
below defined threshold levels (below or equal to 50% for UN GHS Category 2). Coloured
chemicals can also be tested by used of an HPLC procedure. There are three validated
test methods that adhere to this Test Guideline. Depending on the regulatory framework
and the classification system in use, this procedure may be used to determine the
skin irritancy of test substances as a stand-alone replacement test for in vivo skin
irritation testing, or as a partial replacement test, within a tiered testing strategy.