A skin penetration claim is validated by demonstrating that active ingredients effectively pass through the stratum corneum to reach deeper layers such as the epidermis and dermis. This is typically assessed using in vitro techniques like Franz cell diffusion studies, which simulate the skin barrier and measure ingredient absorption. Additionally, techniques such as tape stripping can evaluate penetration depth by sequentially removing skin layers and analyzing ingredient distribution. These in vitro methods ensure that the product’s active ingredients are capable of penetrating the skin barrier and achieving the intended efficacy.