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Comedo

Pronounced - KOM-e-do
Comedo is an acne lesion. (plural: comedones)

Acne-like skin bumps - Comedones are small, flesh-colored, white, or dark bumps that give skin a rough texture. The bumps are found at the opening of a sebaceous follicle (pore).

People with acne frequently have a variety of lesions, some of which are shown in the diagrams below. The comedo is the basic acne lesion, which is an enlarged, plugged hair follicle.

1) Whitehead - Closed Comedo

If the plugged follicle, or comedo, stays beneath the skin, it is called a closed comedo and produces a small, firm, white bump called a whitehead. Whiteheads are made when a hair follicle (root) is plugged with oil and skin cells.

2) Blackhead - Open Comedo

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 surface of the skin. The 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.

3) Papule

A papule is an inflamed acne lesion that usually appears as a small, pink or red raised bump on the skin surface, and can be tender to the touch. There may be one, a few, or many that can pop out on certain parts of the body, usually the face, chest, back, and neck.

Normal Pilosebaceous Unit

Types of Lesions

References:
National Institute of Arthritis and Musculoskeletal and Skin Diseases
National Institutes of Health
January 2006
NIH Publication No. 06-4998
www.niams.nih.gov/