We put our mattresses, and thus, our mattress protectors, through a lot. Yet many people only wash their mattress protector a handful of times, if that. Experts recommend washing your mattress protector once a month for best results and weekly or biweekly if you struggle with allergies. But there are exceptions: mattress protectors on guest beds don’t need the same regular care, and mattress protectors should be washed immediately if there’s a big spill. When the time comes, wash in cold or lukewarm warm on gentle with a mild detergent and tumble dry on low, as heat and harsh chemicals can weaken waterproofing and binding materials.