Although it may occur at any age, acne is most frequently associated with the maturation of young adult males. Part of the normal maturation process involves the production of—or altered expression of—hormones. During adolescence, hormones termed androgens are produced. Androgens stimulate the enlargement of the sebaceous glands and result in the increased production of dermal oils designed to facilitate the growth of facial hair. In females, androgen production is greater around the time of menstruation. Estrogen in females also reduces sebum production. As a result, acne often appears in young women at the time of their monthly menstrual period.
In most cases, acne resolves itself by the time the individual is 20-30 years old.
Contrary to popular myth, acne is not caused or aggravated by eating greasy foods or chocolate. Bacteria play a critical role in the development of acne. The principal bacterial species associated with acne is Proprionibacterium acnes, the other is Staphylocccus epidermidis. These microorganisms normally reside on the skin and inside hair follicles.
The outward flow of oil forces the bacteria to the surface where it can be removed with washing. However, in the androgen-altered hair follicles, the cells lining the cavity shed more frequently, stick together, mix with the excess oil that is being produced, and pile up in clumps inside the cavity. The accumulated material is a ready nutrient source for the Proprionibacterium acnes in the cavity. The bacteria grow and multiply rapidly to produce an acne sore or pustule.
As the numbers of bacteria increase, by-products of their metabolic activities cause additional inflammation. The bacteria also contain enzymes that can degrade the oil from the oil glands into free fatty acids that are irritating to the skin. Various other bacterial enzymes contribute to inflammation (e.g., proteases and phosphatases).
The damage caused by bacteria in acne ranges from mild to severe. In a mild case of acne, only so-called blackheads or whiteheads are evident on the skin. More severe cases are associated with more blackheads, whiteheads and pimples, and also with inflammation. The most severe form, called cystic acne, may produce marked inflammation over the entire upper body, and requires a physician's attention to reduce the bacterial populations.
Manipulating (e.g., squeezing, scratching, or picking) acne pustules can cause deep and permanent scarring. Normally, simply washing the affected area with soap will help dislodge the material plugging the duct. Because estrogen inhibits the development of acne, taking birth-control pills may help alleviate acne in young women. A topical antibiotic may also prove helpful. For deeper acne, injected antibiotics may be necessary.
Although the tendency to develop acne can be passed from parent to child, certain behaviors can aggravate acne outbreak. Acne can be caused by mechanical irritation, including pulling or stretching the skin, as often happens in athletic activities. Because steroid drugs contain androgens, taking steroids can also aggravate acne. Adolescent women who use oil-based cosmetics and moisturizers may develop an aggravated case of acne. Because the bacteria active in acne are normal residents of the skin, there is no "cure" for acne. Rather, the condition is lessened until biochemical or lifestyle changes in the individual lessen or eliminate the conditions that promote bacterial overgrowth.
See also Menstrual cycle.