Definition of Comedo

Comedo: The primary sign of acne, consisting of a widened hair follicle filled with keratin skin debris, bacteria, and sebum (oil). A comedo may be closed or open. A closed comedo (called a whitehead) has an obstructed opening to the skin and may rupture to cause a low-grade inflammatory skin reaction in the area. An open comedo (called a blackhead) has a wide opening to the skin and is capped with a blackened mass of skin debris.


Last Editorial Review: 3/19/2012

Search MedTerms:


Back to MedTerms online medical dictionary A-Z List
Pill Identifier Tool

Need help identifying pills and medications?
Use the pill finder tool on RxList.