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Genetic Factors
Circumstantial evidence exists that acne is in part a genetic, or inherited,
disease. In studies of identical twins twins that develop from one fertilized
egg if one twin had acne, 97 percent of the other co-twins had acne as well. In
the case of no identical twins or twins that develop from separate fertilized
eggs the figure was 50 percent. In other family studies, 80 percent of acne
sufferers had a brother or sister similarly afflicted, and in 60 percent one or
both parents had experienced acne while growing up. There is an impression among
dermatologists that the severest cases of acne occur in those youngsters both
whose parents had acne or where one parent had very severe acne.
What does all this mean? It simply suggests that some unknown trait or factor
can be passed on from parent to that, in the presence of other existing factors,
promotes the development of acne.
Oily Skin
Most people think that acne and oily skin go together. Generally speaking, this
is true. As a group, people with acne do have oilier skin than individuals who
do not. Furthermore, if you do have acne, the severity of the condition seems
roughly to parallel the amount of oil on the skin surface - that is, the oilier
your skin the worse your acne.
Nevertheless, oily skin is not the cause of acne, since there a many sufferers
who have normal or even dry skin and many, many people who have oily skin
without a trace of acne.
Hormones
Hormones are substances that are produced in the body by the endocrine glands
and are carried by the blood to other parts of the body where they act as
chemical messengers and regulate various bodily functions. For example, the
thyroid gland, located in the neck under the Adam’s apple, manufactures and
secretes a hormone called thyroxin, which regulates the metabolism, affecting
such diverse functions as hair growth and the rate of heartbeat.
Androgens (male hormones) are the only hormones that directly stimulate oil
glands to enlarge and produce sebum. But both sexes produce androgens: males in
the testes and adrenal glands, and females in the ovaries and adrenal glands. Of
course, there is a difference in the normal amounts of androgens produced by
each sex. Since acne is associated with enlarged oil glands and oily skin, it
seems likely, then, that androgens are important factors in the development of
the disease.
In contrast, estrogens (female hormones) to some extent block the effects of
androgens on the oil glands, reducing the size of the glands and the amount of
oil produced. Of these two “opposing” hormones, androgens seem to be dominant,
since relatively small amounts of androgens can overwhelm the action of even
large amounts of estrogens. It is important to understand that the majority of
people who have acne, both male and female, do not have abnormal amounts of
these hormones for their age and sex. It may be that the sebaceous glands of
people who have acne react differently, perhaps excessively, to normal amounts
of these hormones in the body.
Some abnormal conditions, such as cysts or tumors of the adrenal or sex glands,
can cause larger than normal amounts of androgens to be produced. When this
occurs in women, they may experience an increase in facial and body hair, a
disturbance in their menstrual cycle, and acne. Obviously, acne occurring in
this situation is merely a symptom of a more serious problem requiring the
specialized attention of a gynecologist or endocrinologist.
The fact that (1) androgens stimulate the oil glands and encourage acne to
happen and that (2) estrogens to some extent block this action has important
consequences when it comes to the treatment of acne in women.
Another group of hormones directly affects the sebaceous glands and therefore
can influence the course of acne. These are the corticosteroids, cortisone like
hormones made by the adrenal glands. Corticosteroids are prescribed widely for
the treatment of conditions ranging from skin rashes to arthritis.
Unfortunately, they sometimes activate the sebaceous glands, encouraging the
development of acne, although it takes relatively large doses of
corticosteroids, taken for a period of weeks, to cause so called steroid acne.
Similarly, the strong corticosteroid creams, ointments, and lotions used by
dermatologists to treat many different skin conditions also can cause acne or
aggravate it, if it is already present.
Blockage of Follicles
The earliest event in the development of acne is the formation of the comedone,
an oily plug that blocks the follicle opening on the skin surface (blackhead) or
forms an obstruction in the follicle underneath the skin surface (whitehead).
Under normal circumstances, the inside of the follicle is lined with cells that
are similar to the cells of the surface layer of the skin, the epidermis. These
cells grow, mature, die, flake off, and are carried to the surface of the skin
by the flow of sebum. People with acne have a defect in the behavior of these
follicle lining cells, which results in their not flaking off in a normal
manner. These cells are not carried to the surface; instead they block the
inside of the follicle, trapping oil and bacteria and forming a comedone.
Why the follicle lining cells behave in this way in some people and not in
others is a mystery, but attempting to correct this defect with medication is a
basic part of acne treatment.
Bacteria
Acne is not an “infection” in the true sense of the word, but bacteria inside of
the acne-susceptible follicles do contribute to acne inflammation. These
bacteria feed on sebum and break up this complex oily material into smaller
molecules called fatty acids. The acne bacteria and the fatty acids attract
white blood cells from the bloodstream and nearby skin into the follicle. The
white blood cells release chemicals that make holes in the walls of the follicle
and allow the contents of the follicle the sebum, dead cells, and bacteria to
leak out into the adjacent skin, creating a local inflammation. When the area of
inflammation is large enough, we see it as a papule, pustule, or acne cyst.
The bacteria that play a role in acne are not strangers to human skin. They are
part of the group of living organisms that are considered normal residents of
the skin and are found in everyone’s follicles. Nevertheless, reducing their
number through treatment can effectively improve if not eliminate the acne.
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