sentences:  These are more expensive than conventional protectors but add the advantages of pressure relief and in the case of the latter, the ability to be washed.Waterproof mattress protectors keep the mattress clean by securing it from absorbing body excretions (such as sweat) or other liquids resulting from spills.These can take the form of flat rubberized flannel pads (commonly used under a bedsheet for infants) or special breathable fitted covers.