When you cuddle up to your favorite pillow, ready to snooze, the last thing you're probably asking yourself is: How clean is this thing? Turns out, if your pillows haven't been washed in the last few months, not very.

That's because each time you rest your head on one, you leave behind skin, hair and bacteria — all of which attract dust mites. And, if you have dust-mite allergies, dirty pillows can be one of the biggest triggers. Even if you're lucky enough not to have allergies, pillows still get dirty. We sweat on them, drool on them and toss them on the floor.

How do you clean them? Simple: You can throw most of them in the washer and dryer. But before you do that, let's go over some basics because not all pillows are made equal.

Is It OK to Wash Pillows in the Washing Machine?

In the case of down, down alternative and polyester fills, you can wash them in the washing machine — unless the label says otherwise. If your pillow still has a care label, follow the instructions on it. But since most of us tear those labels off before the pillows hit the bed, here's a recipe for washing pillows in the washer.

1. Remove pillowcases and pillow covers.
2. Pretreat stains with an enzyme-based laundry stain remover. Let sit at least 10 minutes before washing.
3. Wash in the machine on the delicate or gentle cycle using a tablespoon or less of detergent — too much soap will cause lots of suds, which are difficult to rinse completely. Wash in warm water. If you have bad allergies, wash in hot water, though you may have to replace your pillows more often since the heat breaks down the pillow over time.

Pro tip: If you have a top-load machine with an agitator, place the pillows in vertically. Always wash two pillows at a time to keep the load balanced — and stick to two so water has room to circulate. If you're only washing one pillow, balance it by washing a couple of heavy towels with it.

How Do You Dry Pillows After Washing?

The quickest, easiest way to dry pillows is in the dryer. But heat can break down the fill, so dry on the air-only cycle for 20 minutes at a time until the pillows are dry. Use a couple of clean tennis balls or dryer balls to speed up the process and dry the fill evenly.

You can also hang pillows over the tub or on a clothesline outdoors. Make sure they're completely dry before using them; otherwise, they'll mildew.

How Long Does It Take to Air-Dry Pillows?

It takes several hours to air-dry pillows. If you turn them every two hours, you'll be able to fluff the filling and check for dryness.

How Do You Get Yellow Out of Pillows?

Have your pillows turned yellow, or do they have yellow stains? Thank the urea in your sweat. (Gross.) To get yellow sweat stains out of pillows:

1. Pretreat stains and let sit for at least 10 minutes.
2. Scrub with a soft brush to loosen the stains.
3. Soak your pillow in hot water and oxygen bleach overnight. Then launder as above.

Pro tip: Don't use regular bleach as it will yellow the fabric further.

Can You Put Solid Latex Foam or Memory Pillows in the Washer and Dryer?

No, you can't put foam pillows in the washer. But you can still clean them. Here's how.

1. Remove the pillowcases and pillow covers.
2. Vacuum both sides of the pillow or run them through the air-only cycle in the dryer for 20 minutes.
3. Treat stains using a damp cloth dipped in a solution of mild detergent and water. Lightly rinse with a clean, damp cloth. Be gentle: Wet foam can tear.
4. Let the pillow air-dry or put it back in the dryer on the air-only cycle until all the dampness is gone.

How Often Should I Wash Pillows?

If you have allergies, wash your pillows monthly. Purdue University suggests washing them every three months. Frequency will depend on how much you sweat, drool and eat in bed.

When Should I Replace My Pillows?

The right pillow is hard to find. As a result, most of us have had a love affair with a good pillow at least once in our lives. That makes letting go of them tough.

But, according to the Asthma and Allergy Foundation of America, you should replace them, at the max, every two years. Replace them sooner if they fail the fold test: Fold the pillow in half and hold it for 30 seconds. When you let it go, the pillow should spring back into shape. If it takes a while, or doesn't go back into shape at all, get ready to shop for a new one.

Can I Make Pillows Last Longer?

You can extend your pillow's life by cleaning it regularly. But you can also give it a pillow cover — often found through stores that sell allergy products. These hypoallergenic, protective covers block dust, dirt and all the other yucky stuff that can invade a pillow. You still need to launder the covers and pillows regularly, but protective covers will reduce the amount of pillow wear and tear and extend the life of your pillow.