Educational Content: This article is for informational purposes only and does not constitute medical advice. Always consult a healthcare provider for diagnosis and treatment.
Definition of Comedo
Medically reviewed by Min Clinic Staff | Updated: January 2026
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.