An original procedure for quantitation of cutaneous resorption of sebum

This paper describes an original in vivo device to investigate and quantify cutaneous resorption of sebum. Such a phenomenon was explored using a photometric determination of residual skin surface lipids at different times following initial deposits of known amounts of artificial sebum on demarcated areas. The technique was carried out on seven healthy subjects. The chosen area was the anterior aspect of the forearm, owing to the very low sebum production of this site, less than the sensitivity of the measuring instrument. The kinetics of absorption of applied sebum turned out to be hyperbolic-like and well correlated with experimental results (r = 0.992), allowing a mathematical determination of the initial velocity of penetration of sebum into the skin, reaching 20 micrograms/cm2.min for a standard program including a mean initial deposit of 116 micrograms/cm2. This kinetics actually does not fit with a true percutaneous absorption of lipids but is compatible with that of absorption into the stratum corneum. It conveys the faster absorption of the latter for sebum, a well-known but not so far quantified property of stratum corneum. The model here described is not at once transposable to skin areas with high sebum production since, quite obviously in such zones, the stratum corneum is permanently saturated with skin surface lipids. Therefore, the conclusions of this work cannot be correlated with the regreasing parameters studied so far on the forehead, but they provide interesting data about the evolution of sebum following its output onto the skin surface and therefore a better understanding of sebaceous physiology.