People with acne may have different types of bumps on their skin. These can be whiteheads, blackheads, pimples, and cysts. Where do they come from? Your skin is full of tiny holes called pores. If a pore gets clogged with oil, dead skin, and bacteria, the top surface can darken and you’re left with a blackhead. With a blackhead, the pore stays open. But if the pore closes, a whitehead forms.