How often should you wash a mattress protector?

Wash it every 1 to 2 months under normal use, and more often if you sweat heavily, have allergies, or share the bed with pets. After any spill or accident, wash it immediately. Follow the care label, since the waterproof membrane in many protectors needs a warm, not hot, wash and a low-heat dry to avoid damaging the barrier. Regular washing is the whole point, because it removes the allergens and moisture the mattress cannot shed on its own.