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 pore may close and form a whitehead. If a pore gets clogged but stays open, the top surface can darken and you're left with a blackhead.