What are closed comedones?
Unlike acne that is red and painful, comedones are non-painful pimples that develop over hair follicles. A comedone begins to form when oil and skin cells become trapped in the hair follicle. When that happens, the follicle becomes swollen, causing a bump on the surface of your skin. That bump is a comedone.
There are two different types of comedones: open and closed. In open comedones, sebum, or oil, gets into an open follicle and combines with skin cells and sweat to form a plug. The plug is exposed to air, which oxidizes the plug and gives it a dark appearance. This is also called a blackhead.