From WikiHealth

Causes of acne

Overview of Acne

Acne is a disorder resulting from the action of hormones on the skin�s oil glands (sebaceous glands), which leads to plugged pores and outbreaks of lesions commonly called pimples or zits. Acne lesions usually occur on the face, neck, back, chest, and shoulders. Nearly 17 million people in the United States have acne, making it the most common skin disease. Although acne is not a serious health threat, severe acne can lead to disfiguring, permanent scarring, which can be upsetting to people who are affected by the disorder.

How Acne develops in the skin

Doctors describe acne as a disease of the pilosebaceous units (PSUs). Found over most of the body, PSUs consist of a sebaceous gland connected to a canal, called a follicle, that contains a fine hair (see �Normal Pilosebaceous Unit� diagram, page 2). These units are most numerous on the face, upper back, and chest. The sebaceous glands make an oily substance called sebum that normally empties onto the skin surface through the opening of the follicle, commonly called a pore. Cells called keratinocytes line the follicle.

Normal Pilosebaceous Unit

The hair, sebum, and keratinocytes that fill the narrow follicle may produce a plug, which is an early sign of acne. The plug prevents sebum from reaching the surface of the skin through a pore. The mixture of oil and cells allows bacteria Propionibacterium acnes (P. acnes) that normally live on the skin to grow in the plugged follicles. These bacteria produce chemicals and enzymes and attract white blood cells that cause inflammation. (Inflammation is a characteristic reaction of tissues to disease or injury and is marked by four signs: swelling, redness, heat, and pain.) When the wall of the plugged follicle breaks down, it spills everything into the nearby skin�sebum, shed skin cells, and bacteria�leading to lesions or pimples.

Type of lesions

People with acne frequently have a variety of lesions. The basic acne lesion, called the comedo (KOM-e-do), is simply an enlarged and plugged hair follicle. If the plugged follicle, or comedo, stays beneath the skin, it is called a closed comedo and produces a white bump called a whitehead. 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. Both whiteheads and blackheads may stay in the skin for a long time.

Other troublesome acne lesions can develop, including the following:

Papules�inflamed lesions that usually appear as

small, pink bumps on the skin and can be tender to the touch

Pustules (pimples)�papules topped by pus-filled

lesions that may be red at the base

Nodules�large, painful, solid lesions that are lodged

deep within the skin

Cysts�deep, painful, pus-filled lesions that can

cause scarring.

Causes of Acne

The exact cause of acne is unknown, but doctors believe it results from several related factors. One important factor is an increase in hormones called androgens (male sex hormones). These increase in both boys and girls during puberty and cause the sebaceous glands to enlarge and make more sebum. Hormonal changes related to pregnancy or starting or stopping birth control pills can also cause acne.

Another factor is heredity or genetics. Researchers believe that the tendency to develop acne can be inherited from parents. For example, studies have shown that many school- age boys with acne have a family history of the disorder.

Certain drugs, including androgens and lithium, are known to cause acne. Greasy cosmetics may alter the cells of the follicles and make them stick together, producing a plug.

Factors That Can Make Acne Worse

Factors that can cause an acne flare include:

Changing hormone levels in adolescent girls and

adult women 2 to 7 days before their menstrual period starts.

Friction caused by leaning on or rubbing the skin; many bikers experience this from their bike helmuts as do violinists from the violin rubbing under their chin.
Pressure from bike helmets, backpacks, or tight collars
Environmental irritants, such as pollution and high

humidity

Squeezing or picking at blemishes
Hard scrubbing of the skin.

Myths About the Causes of Acne

There are many myths about what causes acne.

Chocolate and greasy foods are often blamed, but foods seem to have

little effect on the development and course of acne in most people.

Another common myth is that dirty skin causes

acne; however, blackheads and other acne lesions are not caused by dirt. Finally, stress does not cause acne.

Who Gets Acne?

People of all races and ages get acne. It is most common in adolescents and young adults. Nearly 85 percent of people between the ages of 12 and 24 develop the disorder. For most people, acne tends to go away by the time they reach their thirties; however, some people in their forties and fifties continue to have this skin problem.