Dermatologists agree: clogged pores start when oil can’t escape. When sebum overflows and gets trapped under dead skin cells, makeup, or certain heavy ingredients, it becomes the perfect breeding ground for pimples. Some substances are so occlusive they form a seal over your skin, locking in oil and debris. Others mix with your natural oils, making them thicker and harder to flow, especially if you’re already oily or acne-prone.

That’s why comedogenic, or pore-clogging, ingredients matter. On their own, they don’t cause every breakout—but paired with acne-causing bacteria and overactive oil glands, they’re like pouring gasoline on a smoldering fire. Some add excess oil, causing cells to clump instead of shedding. The result: stubborn bumps that won’t quit. Learning which seven ingredients to avoid won’t just clear your pores—it can completely change how your skin behaves.