Acne (acne vulgaris, common acne)
Acne (acne vulgaris, common acne) is a disease of the hair follicles of the face, chest, and back that affects almost all teenagers during puberty -- the only exception being members of a few primitive Neolithic tribes living in isolation. It is not caused by bacteria, although bacteria play a role in its development. It is not unusual for some women to develop acne in their mid- to late-20s. Acne appears on the skin as occluded pores ("comedones"), also known as blackheads or whiteheads, tender red bumps also known as pimples or zits, pustules (bumps containing pus), and occasionally as cysts (deep pimples, boils).
Acne occurs when sebaceous (oil) glands attached to the hair follicles are stimulated at the time of puberty or due to other hormonal changes. Sebum (oil) is a natural substance that lubricates and protects the skin. Associated with increased oil production is a change in the manner in which the skin cells mature, predisposing them to plug the follicular pore. The plug can appear as a whitehead if it is covered by a thin layer of skin, or if exposed to the air, the darker exposed portion of the plug is called a "blackhead." The plugged hair follicle gradually enlarges, producing a bump. As the follicle enlarges, the wall may rupture, allowing irritating substances and normal skin bacteria to get into the deeper layers of the skin, ultimately producing inflammation. Inflammation near the skin's surface produces a pustule; deep inflammation results in a papule (pimple); if the inflammation gets still deeper, it forms a cyst.