Brrr blackheads! They keep coming back. Although they get less while you age. What are exactly blackheads? Blackheads and whiteheads are caused by a buildup of sebum in your pore. Whiteheads form where the oil gets trapped below the surface, while blackheads develop where the blocked oil and skin cells oxidize, turning black. The technical name for a blackhead is an open comedone. There are two different types of comedones: Open (blackheads) and closed (whiteheads). Blackheads are characterized by a dilated opening of a hair follicle, caused by the build-up of sebum, which is oil, P. Acnes bacteria, the primary bacteria responsible for causing acne, and inflammation."