They are made from a soft and comfortable fabric blend of cotton and polyester, woven tightly enough to block out both dust mite and animal dander allergens. (achooallergy)

Cotton/nylon blends have been commonly used as the material for protective clothing, but those blend fabrics are not flame retardant finished because of the unavailability of effective flame retardant finishing systems. (CAT.INIST)

To identify fabric that is unknown, a simple burn test can be done to determine if the fabric is a natural fiber, man made fiber, or a blend of natural and man made fibers. (fabrics.net)