Dermal Corrosion
CeeTox has developed screens that offer alternatives to animal testing in support of the European regulations in REACH and Amendment 7 to the Cosmetics Directive. These in vitro assays produce reliable outcomes at reasonable cost. Two reconstituted human epidermal skin models are used by CeeTox to test for skin corrosion by cosmetic ingredients and chemicals. The OECD 431 protocol is followed for these models.
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Dermal corrosion refers to localized toxic effect resulting from a topical exposure of the skin to a substance. The Globally Harmonized System of Classification and Labeling of Chemicals (GHS) defines skin corrosion as “the production of irreversible damage to the skin; namely, visible necrosis through the epidermis and into the dermis, following the application of a test substance …” (UNECE, Globally Harmonised System of Classification and Labelling of Chemicals, UN, 2003).
CeeTox uses validated 3D skin models to test for skin corrosion. Either raw materials or finished goods can be tested with the models. In addition, histology can be performed to visualize the morphological changes to the models caused by the test compounds. The histological evaluation improves interpretations and reduces false negatives.
The two major mechanisms of skin corrosion are the destruction (erosion or solubilization) of the skin penetration barrier (stratum cormeum) including the viable skin cells underneath, and the rapid penetration of highly cytotoxic chemicals through the skin barrier without involving its destruction.
The in vitro skin model corrosion assay measures cell viability. It is based on the experience that corrosive chemicals show cytotoxic effects following short-term exposure of the stratum corneum of the epidermis. The test predicts and classifies the skin corrosivity potential of a chemical by assessment of its effect on a reconstituted three-dimensional human epidermis model. Cytotoxicity is expressed as the reduction of mitochondrial dehydrogenase activity measured by formazan production from MTT.