A type of acne lesion, which develops when plugs of skin cells and oil become trapped within the hair follicle.
Closed comedones look like bumps on the skin's surface. Sometimes closed comedones have an obvious white head. In other cases, they are skin colored.
Unlike in open comedones (blackheads), the pore opening is obstructed. The oil plug is not exposed to air, so it doesn't take on a brown/black color. If bacteria invade or the follicle wall ruptures, closed comedones can develop into more serious, inflamed acne lesions.
See also milia.