Causes of Acne

Cause of Acne: Bacterial infection of clogged hair follicles

Cause 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. ¹

Triggers list for Acne: The list of triggers mentioned in source as possible causal factors for Acne includes:

• Skin rubbing
• Skin picking or squeezing
• Pollution
• High humidity
• Skin scrubbing
• Menstrual periods - usually 2-7 days before it starts.
• Stress

Cause details for Acne: 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, below). 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.

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.

People with acne frequently have a variety of lesions, some of which are shown in the diagrams below. 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.

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, below). 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.

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. ²

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. ²

Acne pimples form when oil glands make too much sebum, an oily substance. Sebum is made in much larger amounts during and right after puberty than at other times in a woman's life. Sebum then blocks pores to form whiteheads, which form under the skin, and blackheads, which are open to the air. Blackheads are black because the air causes a chemical reaction with the oily debris inside, not because they are dirty. Yeast and bacteria in the skin cause whiteheads to become inflamed, making red, sometimes pus-filled pimples. ³

Hormonal changes can cause acne after adolescence. For instance, many women experience acne during pregnancy. This usually gets better after the baby is delivered and hormonal levels go back to normal. ³

Triggers discussion for Acne: 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
• 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. ¹

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
• 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. ²

Underlying condition causes of Acne: The list of possible underlying conditions (see also Misdiagnosis of underlying causes of Acne) mentioned in various sources as possible causes of Acne includes:

• Excess androgen hormones
• Puberty

Acne as a complication: Other conditions that might have Acne as a complication might be potential underlying causes of Acne. The list of conditions listing Acne as a complication in our database includes:

• Jacobs syndrome
• Puberty

Acne as a symptom: Conditions listing Acne as a symptom may also be potential underlying causes of Acne. The list of conditions listing Acne as a symptom in our database includes:

• Cushing's syndrome
• Diabetes
• Polycystic ovary syndrome
• Puberty
• Type 2 diabetes

Causes of Acne: medical news summaries: The following medical news items are relevant to causes of Acne:

• FDA fails to approve testosterone patch for women
• New topical oil therapy for rosacea and acne developed
• PCOS may be improved by the diet drug Xenical
• Soy allergy sufferers need to be wary of many foods

Related information for causes of Acne: Further relevant information on causes of Acne may be found in the risk factors for Acne and underlying causes of Acne.

Footnotes:
1. excerpt from Health Topics Questions and Answers About Acne: NIDDK
2. excerpt from Questions and Answers About Acne: NIAMS
3. excerpt from Acne: NWHIC

Last revision: May 20, 2003

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