Keratinocytes represent the major cell type in the epidermal layer of the skin. They are highly specialized and play an integral role in maintaining skin physiology and repair by creating a tight barrier to prevent the entry of foreign substances, minimizing the loss of moisture, forming close bonds with the other cells in the epidermis, and acting as an immunomodulator. Human keratinocytes are an excellent tool for investigating the anti-irritation effect of our products as they provide an endless supply of look-alike cells, assuring immense reproducibility in an in vivo (testing on a living organism) environment.