Several factors contribute to the development of acne. The primary problem is the abnormal development of cells inside the hair follicle, leading to the formation of a plug or blackhead (comedo). The plug
disrupts the normal movement of hair, skin cells, and grease (sebum), resulting in enlargement and eventually rupture of the hair follicle. A ruptured hair follicle spills its contents of oil and debris into the skin where it leads to swelling and causes redness (inflammation).
- Propionibacterium acnes, a type of bacteria that normally lives in the skin hair follicles, also plays a role in acne. These bacteria produce substances that cause redness and irritation (inflammation). They also make enzymes, which dissolve the sebum from the oil glands in the skin into irritating substances. These substances also make the inflammation worse.
Certain hormones called androgens are an additional factor in causing acne. Androgens are male hormones that are present in both men and women but are higher in men. Androgens do two things: First, they enlarge the sebaceous glands in the skin. Second, they cause these glands to increase sebum (oil) production. The increased sebum production exacerbates plug formation and serves as more "food" for the bacteria. Androgens surge at puberty, which is why teens
develop armpit and pubic hair and why boys develop facial hair and deeper
voices. This hormonal surge also contributes to the development of acne in
Estrogens, which are the
female hormones, actually can help to improve acne in girls. A woman's
monthly menstrual cycle is due to changes in the estrogen levels in her
body. This is why acne in a female may get better and then get worse as she
goes through her monthly cycle. A doctor may recommend acne treatment with
birth control pills,
which contain the helpful estrogens.
- Because severe acne can run in some families, there seems to be significant hereditary predisposition to serious disease.
Anatomy of the hair follicle: Hair follicles exist on virtually all skin
except for the palms of the hands and soles of the feet. Inside the
follicle, the hair extends up from the deep layers of the skin and comes out
of a pore. Near the surface, the oil gland (sebaceous gland) enters the hair
follicle where it empties sebum at a relatively constant rate. The
sebum lubricates the skin and provides a protective barrier to prevent
drying. Skin on the face, chest, and back has an especially large number of
sebaceous glands. These are the areas where acne occurs.
lesions: There are two major types of acne lesions: noninflammatory and
inflammatory. Noninflammatory acne lesions include blackheads (open
comedones) and whiteheads (closed comedones). Open and closed comedones
along with papules and pustules are referred to as papulopustular acne, a
form of inflammatory acne. Nodular acne is the most severe form of
- Noninflammatory acne: Open comedones result from the enlargement and dilation of a plug that forms from oil and skin
cells inside the hair follicle.
- The hair follicle pore remains open, exposing a
black plug (known as a blackhead). The dark color is not dirt inside the
pore. Instead it is the oil inside the pore, which has become exposed to
the outside air.
- A closed comedo forms if the hair follicle pore remains closed. The plug in a closed comedo or whitehead is therefore not exposed to the outside air, and no black color develops. The closed comedo simply appears as a tiny, sometimes pink bump in the skin.
- Inflammatory acne: Inflammatory acne lesions consist of red blemishes, pimples also called zits (papules, pustules), and larger, deeper swollen tender lesions (nodules).
- Papules are closed comedones, which have become red,
swollen, and inflamed.
- Pustules are closed comedones, which become inflamed
and begin to rupture into the skin, forming pustular heads of various
- Nodules represent large, tender, swollen acne lesions, which have become intensely inflamed and rupture under the skin. If untreated, these can produce deep scarring.
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