For example, I apply petrolatum to my dry hands twice a day as in winter I am usually in a 20-30% RH environment. Within an hour, the petrolatum seems entirely absorbed.
According to , petrolatum and the other oils tested there "do not reach the viable cells of epidermis, saturating only the uppermost horny layers of the skin."
So my question is: Where does the oil go? I do not believe I am shedding unseen skin layers fast enough nor transferring the oil to other objects fast enough that I can repeat and apply twice a day, without the oil going deeper than "uppermost horny layers" and being excreted internally. (Via lymph? blood?) Also, I rarely wash my hands with soap.
 Confocal Raman microscopy for investigating the penetration of various oils into the human skin in vivo. Choe C, Lademann J, Darvin ME. J Dermatol Sci. 2015 Aug. https://atlasofscience.org/oil-penetration-into-the-human-skin/ Accessed 2/8/2019