After two years, dead skin cells, bugs, dust mites, and their droppings make up one-third of your pillow’s weight.

“Washing your pillows is essential,” agrees Chris Brantner, founder of SleepZoo.com, a site that emphasizes the importance of sleep health. “You should be washing them every quarter, or three months.”

Granted, the pillow washing process can be mystifying. Should you stuff your high-end memory foam pillow into a washing machine? Do down pillows need to be dried on the highest setting? Can all pillows be cleaned together? (The answers are no, no, and definitely not.)

While you should always consult the care instructions from your pillow’s manufacturer, these vital cleaning tips from pillow experts will help you rest a little easier.

How to Wash Pillows: A Chore You Should Do Multiple Times a Year

 By Stephanie Booth

Down alternative or polyester pillows

These synthetic pillows tend to be the least expensive, which explains why they also have the least amount of staying power. The life span of a cheap pillow is around 12 to 18 months. A pillow protector can help you get to the far end of that estimate, but two to four times a year, you should still clean it somehow.

To check if your pillow can endure the washer, “fold it in half,” advises Dean Davies, a professional mattress and upholstery cleaner at Fantastic Services in the United Kingdom. “If it doesn’t come back to its original shape immediately, it’s very likely that the pillow won’t survive the cycle.”

If it does snap back, roll it up, using the longer side as a base, then place rubber bands on both ends and the middle. Doing so will minimize the synthetic fibers from clumping in the washer, Davies says.

Wash with mild detergent and warm or cool water, then tumble dry on the lowest heat cycle.

Down or feather pillows

To preserve the life span of your soft, squishy pillow, “cover it with a pillow protector that you wash frequently—at least biweekly,” says Michelle Fishberg, co-founder and CEO of Slumbr, a sleep wellness company that matches pillows to sleep styles. She recommends washing down or feather pillows only twice a year.

Never dry-clean down and feather pillows, Fishberg says. Instead, run them through your washer on a delicate cycle. (Wash two at a time so you don’t unbalance your machine.) Use a mild detergent, but skip fabric softener and bleach. Afterward, dry on a medium heat setting.

“You’ll have to keep drying your pillow past the point where it seemingly feels dry, as the down and feathers can clump up inside,” Fishberg says. Avoid scorching by removing the pillow from your dryer every half-hour. Fluff and allow to cool slightly, then pop it back in.

To maximize fluffiness and prevent the down from sticking together, “add a few wool laundry balls or clean tennis balls to your dryer,” suggests Fishberg. (You can place the balls in a clean sock and tie it up to keep the noise to a minimum.)

Between washings, freshen up your pillow by placing it in the dryer on medium heat for 15 minutes. “Doing so will help kill dust mites and keep it fluffy,” Fishberg says.

Latex and memory foam pillows

Most foam pillows come with a cover, which you should wash and dry two to three times a month, Fishberg says. As for the pillow underneath? It’s made to be hypoallergenic and mold-resistant, so washing it once or twice a year should be adequate.

When the time to clean rolls around, “avoid the washing machine,” says Brantner. The mechanical motion could destroy the shape of your pillow. Instead, submerge your pillow in lukewarm water with a small amount of gentle (preferably unscented) detergent. Gently squeeze out the water, then rinse several times until the water runs clear.

The same kid-glove treatment applies for drying your latex or foam pillow. Let it air-dry, a process that could take up to 24 hours, Brantner says. Set it in front of a fan to speed up the process.

Other cleaning methods

If your pillow isn’t a likely candidate for the washer, fill a spray bottle with a solution that’s one part vodka (any cheap brand will do) and three parts water, suggests Jim Ireland, owner and founder of White Glove Elite, a New York City cleaning agency. Spray your pillow liberally, then allow it to air-dry, ideally in the sun. (You may need to mix up a stronger solution to get out tough odors.)

It may sound strange, but it’s effective. “Alcohol is a powerful sterilizer and antimicrobial,” Ireland explains.

Still, when the day comes—and it will—that  you notice your pillow’s taken on a yellow tinge or grown unmistakably lumpy, “it’s definitely past its prime,” Fishberg says.