HEALTH
Faze Online
Acne
Acne
is a disease that nearly all of us have had to deal with at
sometime or another in our lives. Nearly 17 million people in
the United States have acne, making it the most common skin
disease. Acne is a common, self-limiting, multifactorial disease
involving the sebaceous (oil producing) follicles of the face
and upper trunk. Acne affects approximately 85% of the population
between the ages of 12 and 25. Most teens that get acne have
the milder form, called non-inflammatory acne, and get just
a few blackheads or whiteheads every now and then. But some
people suffer from the more severe form, called inflammatory
acne, and have a constant outbreak covering the face, and sometimes
also the neck, back, chest, and groin. In the United States,
at least 350,000 patients have acne severe enough to require
treatment. Although acne is generally self-limiting and non-life-threatening,
the psychological effect it can have on patients is profound.
This is reflected in the amount of money spent on acne therapy
in the United States each year. Sales of nonprescription acne
medications exceed $100 million annually; with hundreds of millions
of additional dollars spent on prescription acne medications.
Pathophysiology of Acne
The causes of acne are multifactorial and not
completely understood. Theories on the causes of acne include
the role of androgens (hormones), Propionibacterium acnes, sebum
production, and follicle growth. Each of these specific theories
will be discussed in further detail once we have reviewed the
basic pathophysiology of acne.
Acne
is generally limited to the parts of the body that have the
largest and most abundant sebaceous glands - the face, neck,
chest, upper back, and upper arms. These sebaceous glands normally
produce sebum, a substance which moisturizes the skin. Acne
lesions are typically centered about the pilosebaceous follicles,
which open onto the skin surface as the pores of the skin.
Sebaceous
glands develop at puberty in response to androgen stimulation
and are attached to the follicle canal by sebaceous ducts. Acne
is believed to result from a change in the inner lining of the
follicle that prevents sebum from passing through. For reasons
not completely understood, cells from the lining of the follicle
are shed too fast and clump together. The clumped cells plug
up the follicle's opening so sebum cannot reach the surface
of the skin. One of the jobs of the sebum is to carry cells
shed by the glands to the surface of the skin. But because the
excess sebum is blocking the openings of the glands, called
ducts, both cells and sebum accumulate. This mixture of oil
and cells causes bacteria that normally live on the skin, called
Propionibacterium acnes (P. acnes), to grow in the plugged follicles.
These bacteria produce chemicals and enzymes that cause inflammation,
which is a characteristic reaction of tissues to injury and
is marked by four signs: swelling, redness, heat, and pain.
When the plugged follicle can no longer hold its contents, it
bursts and spills everything onto the nearby skin - sebum, shed
skin cells, and bacteria. Lesions or pimples develop as a result
of the skin's being irritated.
Individuals
with acne may have a variety of lesions. The basic acne lesion,
called the comedo (kom¢-e-do), is simply an enlarged hair
follicle plugged with oil and bacteria. This lesion is often
referred to as a microcomedo because it cannot be seen by the
naked eye.
If
the plugged follicle, or comedo, stays beneath the skin, it
is called a closed comedo or whitehead. Whiteheads usually appear
on the skin as small, whitish bumps. A comedo that reaches the
surface of the skin and opens up is called a blackhead because
it looks black on the skin's surface. This black discoloration
is not due to dirt but rather to the oxidation of melanin pigment.
Both whiteheads and blackheads may stay in the skin for a long
time.
Other
acne lesions which can develop, include the following:
Papules
- inflamed lesions that usually appear as small, pink bumps
on the skin and can be tender to the touch
Pustules (pimples) - inflamed, pus-filled lesions that
can be red at the base
Nodules - large, painful, solid lesions that are lodged
deep within the skin
Cysts - deep, inflamed, pus-filled lesions that can cause
pain and scarring
ACNE
CAUSES
The exact cause of acne is unknown, but physicians
believe it results from several related factors.
Potential causes include:
- role
of androgens (hormones)
- Propionibacterium
acnes (P. acnes)
- sebum
production
- follicle
growth
Role
of Androgens
Androgens (male sex hormones) stimulate growth
of sebaceous follicles and enhance production of sebum. After
puberty, boys produce 10 times as much androgen as girls; therefore
it is not surprising that more boys than girls develop severe
cases of acne. During the second decade of life, sebum production
closely parallels both androgen production and the presence
of acne. Although testosterone is the most potent androgen,
its metabolites and weaker androgens are increased in acne patients
and may stimulate sebaceous gland activity.
Sebum Production
Sebum is produced in the sebaceous glands and
consists of glycerides, wax esters, squalene, and cholesterol.
At times, a relationship between increased sebum secretion and
severity of acne is present. The glyceride component of sebum
is converted to free fatty acids (FFA) and glycerol by lipases,
products of P. acnes. FFA may irritate the follicular wall and
cause increased cell turnover and inflammation.
Follicle Growth
Abnormal alterations in the follicle wall and
its cell growth (keratinization) have also been associated with
acne. The increased production of loosely adherent keratin cells
has been correlated with obstruction of the follicles seen in
comedo formation. Whether this abnormality is inherent or secondary
to other factors is unknown.
Bacteria
P. acnes is part of the normal flora in the sebaceous
follicle and plays an important role in the initial development
and maintenance of the inflammatory response present in acne.
Although
P. acnes counts are typically higher in patients with acne,
and antibiotic therapy reduces these count, the pathogenic role
of P. acnes is not that of simple infection. P. acnes may be
capable of causing increased antibody formation, thereby leading
to an inflammatory response. Although the exact cause of acne
is unclear, its pathogenesis involves many factors that are
interrelated.
Other Potential Causes
Hormonal changes related to pregnancy or starting/stopping
birth control pills can also cause acne. Stress, particularly
severe or prolonged emotional tension, may aggravate acne. Certain
drugs, including androgens, lithium, and barbiturates are known
to cause acne. Greasy cosmetics may alter the cells of the follicles
and make them stick together. Friction caused by leaning on
or rubbing the skin or the pressure of bike helmets, backpacks,
or tight collars can contribute to or worsen acne. Also, environmental
irritants (such as pollution and high humidity), squeezing or
picking at blemishes, and hard scrubbing of the skin can make
acne worse.
Acne Myths
In addition to the potential causes of acne,
there are also many myths about what causes acne. Chocolate
and greasy foods are often blamed, but research has shown that
foods seem to have little effect on the development and course
of acne in most people. Another myth is that dirty skin causes
acne; however, blackheads and other forms of acne lesions are
not caused by dirt.
So,
just to reiterate what we have discussed in the background section
on acne;
Acne
is the most common skin disease in the U.S., affecting approximately
85% of the population between the ages of 12 and 25
Acne is thought to be, in part, the result of oil glands at
the base of the hair follicles which become overactive during
teenage years as a result of hormonal changes
Causes of acne are multifactorial and include: role of androgens,
P. acnes, sebum production, follicle growth
Skin cells can "plug" skin pores causing whiteheads,
which stay below the skin and blackheads, with reach the skin
surface
A "pimple" is an oil gland that is infected with bacteria,
resulting in an inflamed area with pus formation
Acne is NOT caused by eating oily foods, soda, or chocolate
