India, June 18 -- W e pay close attention to expiration dates on food, medicines, and skincare products, but have you ever wondered if your pillow has a lifespan too? Over time, pillows can accumulate dust, allergens, and bacteria while losing their shape. "Many pillows use synthetic materials, such as polyurethane foam, which can break down over time and release harmful compounds," says orthopaedic surgeon Dr Rahul Modi. He adds, "Prolonged exposure to a dirty pillow can lead to lung infections. You should replace your pillows after a certain interval, otherwise it can harm your health." A pillow's lifespan largely depends on its material. Here are five common types of pillows and how long they typically last, as per Dr Modi. Dr Modi says that when choosing a pillow, consider your sleep position, body type, and preferred material. The right pillow should keep your head, neck, and spine properly aligned....