Unless your pillow specifies that it's "spot-clean only," you can likely wash it in the washing machine on a gentle cycle. For long-lasting support, they should only be washed every 6 months. The detergent you use should be free of dyes and perfumes to prevent allergic reactions. And if you have a down pillow, you should wash it with a small amount of powder detergent as the liquid can stick to the feathers—leaving residue that may cause clumping. Pillowcases should be washed weekly.