Comedone
Comedones can be divided to open (blackheads) or closed (whiteheads).Blackheads are clogged hair follicles, in which you will find excess sebum, dead cells or dirt from the skin surface. All this creates an ideal environment for the growth of microorganisms and possible inflammation. Open comedones react with the surface of the skin, and it is the oxidation after contact with the air that determines their typically black color.
White pimples are a type of acne that usually appears on the skin in the form of small, round, white bumps. This type of acne is caused by excretion of sebum from the skin and dead skin cells that clog the pores on the skin.
Thus, white pimples block the pores, while in black pimples the pores remain open.