Chemicals that cause dermal irritation are known to induce alterations in the structure of keratin, collagen and other dermal proteins. The Dermal Irritection Assay System is an in vitro test that mimics these biochemical phenomena.
This test also consists of two components:
- A membrane substrate that has been modified by covalently crosslinking a mixture of keratin, collagen and an indicator dye to it and;
- A reagent solution consisting of a highly organized globulin/protein macromolecular matrix.
Application of an irritant chemical to the membrane disc disrupts the ordered structure of keratin and collagen and results in release of the bound indicator dye. Additionally, dermal irritants induce changes in conformation in the globular proteins found in the reagent solution.
The extent of dye release and protein denaturation may be quantitated by measuring the changes in optical density of the reagent solution at 450 nm (OD450).
Comparison of these optical density measurements to those produced by standard chemical irritants permits calculation of an "irritancy score" that has been shown to be directly related to the potential dermal irritancy of the test material.