Acne is a chronic, inflammatory skin disease that results in whiteheads, blackheads, pimples, cysts, and nodules. It is not dangerous, but it can leave skin scars.
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.
They tend to appear on the face, back, chest, shoulders, and neck.
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.