4-n-butyl resorcinol (4-nBR) is a highly effective tyrosinase inhibitor, and can be used in cosmetic product for depigmentation purpose. Its efficacy correlates with 4-nBR that absorbed by skin. In this study, skin distribution of 4-nBR within either human or pig skin ex vivo was studied and compared by three independent laboratories. Good agreement was observed in each compartment considering usual inter-lab variability. The percutaneous absorption and skin distribution studies were carried out by L'Oréal (lab A), Fudan University (lab B), and Medicilon (lab C). 

Reference:

Yang Liu, et al. Inter-laboratory study of the skin distribution of 4-n-butyl resorcinol in ex vivo pig and human skin. J Chromatogr B Analyt Technol Biomed Life Sci. 2018 Sep 1;1093-1094:77-79. doi: 10.1016/j.jchromb.2018.06.048.