Dried plugs of
fatty material in the
ducts of the sebaceous (oil-secreting) glands. Also known as
comedowns. The black
color at the surface of the plugs is not dirt, as often believed;
albinos (who lack the pigment
melanin) have light-colored "blackheads."
The
blackhead is produced by
faulty functioning of the
sebaceous follicle as it
releases sebum, the fatty
secretion of the sebaceous glands. The consequent obstruction to the gland leads to enlargement of the
follicle's opening. Infection by
bacteria living on the skin may lead to
inflammation and so to the characteristic
papules, or "pimples," of
acne.