There are hard black things in the pores, and this condition may be blackhead pimples. Blackheads are formed mainly due to overactive sebaceous glands. If the sebum secreted by the active sebaceous glands cannot be effectively discharged from the surface of the skin, it may accumulate inside the sebaceous ducts. If a certain amount of sebum is formed, it may collect together and form hard bumps. Sometimes, because the surface of these bumps is exposed to the skin, the oxidation of air or dust and impurities leads to a black appearance, which is commonly referred to as blackheads. For blackhead pimples there are large and small ones, and if there are large ones they may gradually develop into sebaceous cysts. Because the walls of the cysts gradually expand and eventually become infected, they may sometimes be accompanied by painful symptoms.