Did you know that by the time your pillow is two years old, half its weight may be comprised of dust mites and skin cells, along with mold or mildew? YUCK. That disgusting fact alerted me that it’s time to replace our pillows. You too? First, I decided to do a little research—and save you the trouble!

Pillows affect sleep quality and how well we rest/recharge. Experts warn that the wrong pillow may contribute to neck and lower back pain, sneezing, and arm or shoulder soreness. Here’s a quick way to see if yours is past its prime:

Do a fluff test. A fluffy pillow means that fresh air can travel through it, which provides better cushioning and support. Fold your pillow in half to see if it unfolds on its own within 30 seconds.

Mine are definitely sluggish. That seals the deal: it’s time to go shopping!

I asked my chiropractor, who treats my chronic neck and shoulder stiffness, what to consider. He explained that you want to sleep with your head in neutral alignment, i.e., not leaning too far forward or back. The key is matching your pillow to your sleep position, which may mean that you and your partner need different types:

Back Sleepers need medium support. If the pillow’s too thick it pushes your head too far forward. If it’s too soft, your head sinks down to the mattress. Extra thickness and firmness in the bottom third will cushion your neck, and a pillow you can smoosh around lets you find the right level of comfort.

Side Sleepers need a firm or super firm pillow to help support the neck. A thicker pillow provides an even sleeping surface to help keep your head, neck and shoulders in a horizontal line.

Stomach Sleepers may not even want a pillow. If you do, choose one that’s soft and fairly flat to keep your neck in line with your spine and prevent extreme turning to either side. Placing a pillow under your stomach may help avoid lower back pain.

Mixed Sleepers (that’s me): People who shift sleeping positions during the night do well with a medium-thick pillow you can move around. If you usually wind up on your stomach, go softer.

Confirm your preferred position:

1. When you’re about to fall asleep, spend a few minutes in different positions to see which feels most comfortable. If you lie on your back for a half hour and don’t nod off, for example, chances are that’s not your favorite.
2. Notice your position when you wake up, and keep a list so you can compare over a few days.

Fill ‘er Up: There’s a seemingly endless variety of materials and terminology. Some experts suggest having a pillow “wardrobe” to meet different needs, but that can get awfully expensive. If you generally prefer a soft pillow but suffer from occasional neck pain, try using a travel or throw pillow to add extra support.

Down: Soft, lightweight and lofty, down—the inner plumage of ducks and geese—is the most luxurious of all fills and often the most expensive. “Loft” refers to the height of a pillow when it lies flat; i.e., low loft is thin and high is thick. “Firm” is industry-speak for compact while “plush” is pillow talk for cushier. If you want one that’s tall and squishy, for instance, pick “high loft, plush.” “Low loft, firm” will be thinner and more dense.

A natural insulator, down is resilient, breathable, can be moved around to give you support where you need it, and lasts longer than synthetic fills. The best pillows are supposed to last ten years. However, if you’re going to replace them after two years anyway, why spend a ton?

Fill power measures the volume of a single ounce of down, and more down equals more comfort and insulation. Look for fill power of at least 500. Below that level, the fill may contain a lot of feathers or small, damaged down clusters that won’t stay fluffy.

Feather vs. Down/Feather: Feather pillows aren’t as soft as down, and quills can poke through the fabric. A 50/50 mix is a better bet: it combines the softness of down with the firmness and springy support of feathers. Use pillow protectors to avoid getting jabbed!

Note: I’ve read that there’s no scientific evidence that down or feather pillows exacerbate allergies or asthma but there are lots of synthetic options if you don’t want to take a chance or have ethical concerns.

Down Alternative Fill is made of synthetic or natural fibers designed to mimic the luxurious feeling of down at a lower price. Brand names include Primaloft® and Down-Free™.

Like down alternative, synthetic fills such as polyester are hypoallergenic and machine washable.

Made from polyethylene and other chemicals, memory foam is a dense, sponge-like material that continually molds and adjusts to your head and neck. Pillows come in various shapes and offer good support, especially if you have issues with your neck, shoulder or spine.

New memory foam usually has a chemical odor, which may give you a headache. Before putting them on your bed, let the pillows air out for a few days in another room. Memory foam pillows don’t “breathe” and tend to retain heat. They’re best if you don’t move around a lot since they won’t adapt quickly to a different position.

Foam: Look for higher density to reduce breakdown and maintain support.

Latex pillows, made from the sap of rubber trees, are firm, elastic, resilient and come in different shapes. Latex resists mold and dust mites and may improve back and neck alignment, as pillows are often contoured for neck support. They stay cooler than memory foam but don’t have as much “give”, and they tend to be heavy as well as expensive.

Wool and cotton pillows aren’t susceptible to mold and dust mites so they’re another option for allergy sufferers. They’re generally quite firm—not the best choice if you’re a stomach sleeper or like a squooshy pillow.

Specialty pillows, designed for specific needs, may be helpful but research is inconclusive and they’re often costly. Caveat emptor!

• Cervical pillows have extra cushioning in the bottom for neck support.
• Water pillows can be customized for density and support, so they’re often recommended by chiropractors and physical therapists.
• Cool pillows may be helpful for hot flashes and night sweats.
• Oxygen-promoting pillows claim to increase oxygen in the blood by up to 29% to help you breathe more deeply.
• Anti-snore pillows are designed to lift the chin to keep airways open. Worth a try if your significant other is keeping you awake!
• Positional pillows claim to help people with sleep apnea stay in an ideal position and reduce tossing and turning during the night.

A few things to keep in mind:

• More expensive isn’t necessarily better.
• Higher thread count (minimum 300; experts recommend 500-800) means a pillow will feel plusher and be more durable.
• Try before you buy. If you can’t lie down in the store (and don’t mind looking a little weird!) stand next to a wall in your usual sleep position with your head against the pillow, and ask someone to check if your head is tilting one way or another. It should align with your spine.

I’m dreaming of a good night’s sleep with some fresh, new pillowzzzzz!