What is a “comedo,” and what does it have to do with acne?

Dr. Michael Roizen, MD
Internal Medicine

A comedo is not a karate move, but that doesn’t stop us from attacking it with a vengeance. A comedo (plural comedones) is a small bump on the skin that can be black or white, large or small, one or many that typically occurs on the forehead and chin. It is a plug of sebum, the oily substance that is produced by glands in your skin, with a little skin protein and dead skin cells mixed in. If it is open, it is called a blackhead (open comedo), and if it is closed, it is a whitehead (closed comedo). Did you know that the black isn’t actually dirt? It’s a mixture of keratin and sebum that darkens as it oxidizes.

Comedones are different from acne in that the surrounding tissue doesn’t become inflamed or contain pus or bacteria. However, the bumps occur because of the same, frustrating problem: a pore plugged with sebum.

Dr. Mehmet Oz, MD
Cardiology (Cardiovascular Disease)
A comedo is the medical term for a blackhead or whitehead, acne lesions that form when your pores get blocked. When the pore is completely closed, a whitehead or closed comedo forms. When the pore is clogged but remains open at the surface, a blackhead or open comedo forms. Pimples form when the blockage occurs deeper within your skin. The deeper the blockage, the more likely pus will fill the pimple. Painful cysts or nodules, the most severe type of acne lesions, form deep under the skin.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.