Although most pillows have a tag giving laundering instructions, few people bother to wash them. We think they're shielded from the day-to-day grit and grime of life, thanks to the pillowcase. Or else, that washing them may ruin them. But, the standard pillowcase is typically only made of cotton or some other easily permeated fabric, rendering the pillow susceptible to pretty nasty stuff. Regular close-proximity exposure to any of these contaminants, or others like pet dander, can cause illness or allergies to flare up. It's no small amount of junk, either. The good news is that laundering pillows is a surprisingly easy task. Martha Stewart says you'll only need to wash the pillows twice per year, although the protectors themselves require monthly laundering. But there could be times when you need to launder your pillow more frequently. Mary Zeitler, consumer scientist with Whirlpool Corporation's Institute of Home Science. Ditto that if you deep sleep solution with a pet or have recently had a cold or other contagious illness.