AllerRest Fabric protector blocks dust mites. The material is 100% cotton AllerRest Fabric specially woven to block dust mites and allergens from penetrating through to the pillow. An ideal pillow protector for any pillow. This pillow protector has a concealed zipper for a tidy look. This Approved American Lung Association partnership product boasts a 300 thread count AllerRest Fabric to block dust mites and a zippered closure for increased structural support.