Pillowcases can significantly contribute to acne for a couple of reasons. First, they absorb oils, sweat, and dead skin cells from your face and hair. Over time, these residues build up and can clog pores, creating a breeding ground for bacteria that cause acne. If the pillowcase is not changed frequently, this accumulation becomes more substantial, increasing the risk of breakouts, particularly for those who are already prone to acne. Dermatologists often recommend using a fresh pillowcase every two to three days to help manage and reduce acne.