What Is Acne? Acne is a disorder resulting from the action
of hormones on the skin's oil glands (sebaceous glands),
which leads to plugged pores and outbreaks of lesions
commonly called pimples or zits. Acne lesions usually
occur on the face, neck, back, chest, and shoulders.
Nearly 17 million people in the United States have
acne, making it the most common skin disease. Although
acne is not a serious health threat, severe acne can
lead to disfiguring, permanent scarring, which can
be upsetting to people who are affected by the disorder.
How Does Acne Develop? Doctors describe acne as a disease of the
pilosebaceous units (PSUs). Found over most of the
body, PSUs consist of a sebaceous gland connected
to a canal, called a follicle, that contains a fine
hair (see "Normal Pilosebaceous Unit" diagram,
below). 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 diagrams below. The basic
acne lesion, called the comedo (KOM-e-do), is simply an
enlarged and plugged hair follicle. If the plugged follicle,
or 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
a blackhead because it looks black on the skin's surface.
This black discoloration is not due to dirt. Both whiteheads
and blackheads may stay in the skin for a long time.
Types of Lesions
Other troublesome acne lesions
can develop, including the following:
Papules--inflamed lesions that usually appear as
small, pink bumps on the skin and can be tender to
the touch
Pustules (pimples)--papules topped by pus-filled
lesions that may be red at the base
Nodules--large, painful, solid lesions that are
lodged deep within the skin
Cysts--deep, painful, pus-filled lesions that can
cause scarring.
Acknowledgments: The NIAMS gratefully
acknowledges the assistance of Robert Katz, M.D., Rockville,
MD; Larry Miller, M.D., Chevy Chase, MD; Alan Moshell,
M.D., NIAMS, NIH; Gary Peck, M.D., Washington Hospital
Center, Washington, DC; and Maria Turner, M.D., National
Cancer Institute, NIH, in the preparation and review of
this booklet. Article
syndicated from National
Institute of Arthritis and Musculoskeletal and Skin Diseases
NIH Publication No. 01-4998 Publication Date: October
2001
