Dermatologists suggest replacing pillows every 1-2 years to maintain hygiene and skin health. Over time, pillows accumulate dust mites, dead skin cells, and oils, which can trigger allergies or skin issues, said cosmetologist Dr Karuna Malhotra, founder of Dr Karuna's Cosmetic Skin & Homeo Clinic. She reiterated that using an old pillow can contribute to acne and skin irritation.