There are a number of factors that cause the follicles to become
clogged and infected. One important factor is the overproduction
of androgen. Androgen is a chemical, or male sex hormone,
that both males and females normally produce. However, hormonal
changes in the body during puberty, pregnancy, or the female
menstrual cycle cause some people to produce higher than
usual levels of androgen. Although scientists are unsure why, excess
androgen stimulates the sebaceous oil glands inside the follicles
to enlarge and manufacture excess amounts of oil called
sebum. Whereas the normal production of sebum is necessary
for healthy skin, excess sebum leads to the development of acne.
Normally, the sebaceous oil glands produce small amounts of
sebum, whose job it is to moisten and protect the skin. In order to
do this, sebum works its way up through the hair follicles, where
it washes away dead cells that accumulate in the follicles. Then sebum
empties onto the skin through tiny openings in the follicles
called pores. Here sebum protects the skin from bacteria that live
on the skin by washing the bacteria away.
However, when excess sebum is produced, it accumulates in
the follicles rather than spilling out onto the surface of the skin.
This occurs because the follicles are extremely small and narrow.
Therefore, large volumes of sebum cannot pass through the follicles to the surface of the skin at the rate the sebum is produced. Instead,
sebum becomes trapped in the follicles, where it mixes with
dead skin cells, forms sticky plugs that block the pores, and prevents
sebum from reaching the surface of the skin. As a result,
the skin around the clogged follicles dries out. At the same time,
since not every follicle becomes clogged, excess oil that spills onto
the skin through unclogged follicles causes the skin to feel oily. Therefore, a person with acne may have dry skin around clogged
follicles and oily skin everywhere else.
Worse yet, without sebum to wash away bacteria on the skin,
bacteria grow and multiply around the clogged follicles. Eventually,
bacteria get inside the clogged follicles, where they mix with
sebum and dead cells and cause an infection. This most commonly
occurs on the parts of the body that have the largest sebaceous
glands, such as the face, chest, neck, shoulders, upper back, and
buttocks. The result is the development of one type of acne lesion
known as a comedone.
Source: Acne / by Barbara Sheen.
