• MEDICAL CONDITION
ACNE

Acne

Synonyms: Pimples, Zits

DESCRIPTION

Acne is a disorder resulting from the action of hormones and other substances on the skin’s oil glands (sebaceous glands) and hair follicles. These factors lead to plugged pores and outbreaks of lesions commonly called pimples or zits. Acne lesions usually occur on the face, neck, back, chest, and shoulders. Although acne is usually not a serious health threat, it can be a source of significant emotional distress. Severe acne can lead to permanent scarring.

Doctors describe acne as a disease of the pilosebaceous units (PSUs). Found over most of the body, pilosebaceous units consist of a sebaceous gland connected to a canal, called a follicle, that contains a fine hair (see illustration “Normal Pilosebaceous Unit”). 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 illustrations below. The basic acne lesion, called the comedo (KOM-e-do), is simply an enlarged and plugged hair follicle. If the 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 an open comedo or blackhead because it looks black on the skin’s surface. This black discoloration is due to changes in sebum as it is exposed to air. It is not due to dirt. Both whiteheads and blackheads may stay in the skin for a long time.

www.ninds.nih.gov/disorders