It is important to note that there are three components relating to functional measurements of sebaceous gland activity . The first is the rate of synthesis of sebum, referred to as sebum production; the second component is  its  delivery through  the pilosebaceous duct - the follicular reservoir - and,  the third, the excretion of sebum onto the skin surface, technically called sebum excretion.  Methods are now available to measure these three interrelated functions.

  Note that the term 'casual level' refers to a random collection  of lipid from the  skin surface without any prior preparation of the  skin. This is a measure of the sebum excretion and the lipid which has accumulated since the skin was last washed. Casual level techniques are no longer recommended for in-depth physiological studies of  the sebaceous system.  All techniques for measuring either sebum excretion or sebum production require some preliminary preparation of skin to remove the casual lipid remaining on the skin from when the skin  was last  touched  or washed. Such  techniques include the  use of absorbent papers or wiping of the skin  surface with gauze soaked in an organic solvent such as ether or hexane. This latter technique may also remove some of the sebum from the  storage/delivery area, i.e. from the upper part of the pilosebaceous duct.

  Histological  techniques  have been  widely  used  to assess the function of the sebaceous gland but other techniques are preferred. The size of glands are analysed  either by  planimetry or by using  a  computerassisted device such as the Magiscan. More recently, Simpson  et  al  have  used  individual sections  of sebaceous  glands and,  by incubating them  with radiolabelled precursors, have been able to relate the metabolism of hormones with size of the glands. This technique will be discussed.