Comedo

Plug of dried, discolored fatty matter clogging a pore of the skin; commonly called a black-head.

A blackhead, as seen in acne.

A small point of dark, hard matter in a sebaceous follicle, often found associated with acne on the skin of adolescents.

Comedones, accumulation, in a hair follicle or oil gland, of dead cells and oily substance; the basic lesion m acne vulgaris; commonly called blackhead.

The typical small skin lesion of acne vulgaris and seborrheic dermatitis. The closed form is called a whitehead. It consists of a papule from which the contents are not easily expressed. When inflamed these lesions form pustules and nodules. The open form of comedo, called a blackhead, is rarely inflamed. It has a dilated opening from which the oily debris is easily expressed. Both forms are usually located on the face, but the chest and back may be involved.