What do sebaceous glands secrete?

Sebaceous glands are found in the skin, often in
association with a hair follicle. They occur over the entire body except for the palms
of the hands and the soles of the feet. The task of sebaceous glands is the creation and
release of sebum, a complex, waxy or oily substance with a number of functions. Sebum
helps to make the epidermis waterproof, which allows the body to control water loss;
this water resistance also helps the skin to be a good barrier to infection. Sebum also
helps maintain the flexibility of hair shafts, and in the ear canals it functions as a
dust catcher to prevent particles or tiny insects from reaching the
eardrum.

The volume and composition of sebum varies with
age and hormonal status.