Whiteheads, blackheads, pimples, cysts, and nodules are all types of acne. It is the most common skin condition in the United States, affecting up to 50 million Americans yearly. It commonly occurs during puberty, when the sebaceous glands activate, but it can occur at any age. It is not dangerous, but it can leave skin scars.
The glands produce oil and are stimulated by male hormones produced by the adrenal glands in both males and females. At least 85 percent of people in the U.S. experience acne between the ages of 12 and 24 years.
Human skin has pores that connect to oil glands under the skin. Follicles connect the glands to the pores. Follicles are small sacs that produce and secrete liquid.
The glands produce an oily liquid called sebum. Sebum carries dead skin cells through the follicles to the surface of the skin. A small hair grows through the follicle out of the skin.
Pimples grow when these follicles get blocked, and oil builds up under the skin.
Skin cells, sebum, and hair can clump together into a plug. This plug gets infected with bacteria, and swelling results. A pimple starts to develop when the plug begins to break down.
Propionibacterium acnes (P. acnes) is the name of the bacteria that live on the skin and contributes to the infection of pimples.
Research suggests that the severity and frequency of acne depend on the strain of bacteria. Not all acne bacteria trigger pimples. One strain helps to keep the skin pimple-free.
A range of factors triggers acne, but the main cause is thought to be a rise in androgen levels. Androgen is a type of hormone, the levels of which rise when adolescence begins. In women, it gets converted into estrogen. Rising androgen levels cause the oil glands under the skin to grow. The enlarged gland produces more sebum. Excessive sebum can break down cellular walls in the pores, causing bacteria to grow.