Is the excretion of sebum regulated?

The kinetics of sebum excretion on the forehead of volunteers were measured over a period of at least 7 h. The transmission data obtained by the ground glass method were transformed into weight (sebum/cm2). The excretion time function can be described by the equation: w = A . (1 - B . e -C.t). This nonlinear function is typical for modes of excretion in the biological field. Regulation of sebum excretion is probable. Objections against such regulation by feedback were discussed.