Pillow protectors are covers that fit over a pillow to protect it from spills, stains, and allergens. They are usually made of a breathable material such as cotton or polyester and have a zipper or other closure that allows them to be easily removed and washed. Pillow protectors can extend the life of a pillow by keeping it clean and fresh. They are also a good option for people with allergies or asthma, as they can help to reduce exposure to dust mites and other allergens.