This test is performed according to the Organization for Economic Co-operation and Development (OECD) test guideline number 439 and allows for proper labelling of the test compound or xenobiotic according to United Nations Globally Harmonized System (UN GHS) Classification and Labelling of Chemicals.1
Historically, dermal irritation was performed on rabbits using the Draize Skin Test.2 However, three dimensional human epidermis tissue equivalents have been developed and validated as replacements for the Draize skin test. These 3D tissues are dermal epithelia grown from normal human keratinocytes and are extremely similar to native human epidermis, both metabolically and morphologically, including the stratum corneum. In addition, the apical surface is direct contact with the air (tissue is fed basally) allowing for testing of almost all types materials, such as gels, creams liquids and powders, regardless of aqueous solubility.
In this assay, MatTek EpiDerm™ tissues are exposed on the apical surface to neat (undiluted) test chemical for 30 minutes and the viability of the tissue is then determined via the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. This data is then normalized to the negative control and ocular irritation is determined based on the viability using the following table:
|Mean Tissue Viability||In Vivo Prediction|
|≤ 50%||Irritant (H315)|
|> 50%||Non-Irritant (No Category)|
Additionally, the protocol can be adapted in order to assess irritation potency (mild, moderate, severe etc.) of test chemicals by determining the ET50 over a 24 hour exposure period.