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If you've been diagnosed with dust mite allergies, your doctor has probably told you to encase your mattress and pillows in allergy-proof covers. Great advice. But then you go online and encounter terms like "pore size," "microfiber," "micro-weave," and "laminated" — and suddenly a simple purchase feels like a science exam.
We field calls about this every day. Let's clear it up once and for all.
Why Allergy Bedding Works
Dust mites, their feces, pet dander, mold spores, and pollen all collect in fiber surfaces — your mattress, pillows, and duvet are effectively allergen reservoirs. You can't see, feel, or smell these particles, but every time you move in bed, you puff them into the air and breathe them in all night.
Allergy-proof covers create a physical barrier between you and those allergens. If you can't breathe them in, they can't make you sick. Paired with weekly hot water washing of your sheets and pillowcases, a good set of encasements dramatically reduces your allergen exposure from the very first night.
Two Ways to Make a Fabric Allergy-Proof
There are two fundamentally different approaches to building an allergen barrier into a fabric — and understanding the difference makes choosing the right cover much easier.
1. Micro-Weave Fabrics
A micro-weave fabric is woven so tightly that the spaces between the fibers — the pore size — are too small for allergen particles to pass through. The fabric itself is the barrier. No coating, no membrane. Just an exceptionally tight weave.
Pore size is measured in microns (one micron = one millionth of a meter). For context, a human hair is about 70 microns wide. Dust mite allergen particles — their fecal matter and body fragments — are up to 10 microns in size. Pet dander particles run around 3 microns. Standard cotton sheets have pore sizes in the hundreds of microns, which is why dust mites pass right through them.
For a micro-weave fabric to be effective against dust mites, its pore size must be 10 microns or smaller. All of our AllergyCare™ micro-weave fabrics are well below this threshold.
2. Laminated / Membrane Fabrics
A laminated fabric bonds a urethane membrane to the back of the base fabric using heat. It's the membrane — not the fabric — that provides the allergen barrier. Because the membrane is a complete, impenetrable layer, laminated covers don't have a pore size. They block everything, including liquids, making them fully waterproof as well.
The trade-off is feel and breathability. Laminated covers tend to run warmer than micro-weave covers because the membrane reduces airflow. For most adults, micro-weave is more comfortable for everyday sleep. For children's beds or situations where waterproof protection is needed, laminated covers are the right choice.
Pore Size and Fiber Type: Why Cotton and Polyester Are Different
Not all micro-weave fabrics are the same — and fiber type is the main reason why.
Polyester is a very strong synthetic fiber. Because it's so strong, it can be woven much more tightly than natural fibers without breaking. This means polyester micro-weave fabrics can achieve smaller pore sizes.
Cotton fibers are naturally softer and more flexible, but they're not as strong under tension. You can't weave cotton as tightly as polyester, so all-cotton allergy covers will always have a slightly larger pore size than equivalent polyester fabrics. That said, our cotton fabrics are still well within the effective range for dust mite protection.
Organic cotton adds another consideration: it's grown without synthetic pesticides or fertilizers and processed without dyes or chemical treatments. This makes it the right choice for people with chemical sensitivities — even though its pore size is slightly larger than conventional cotton.
Our AllergyCare™ Fabric Lineup: Pore Sizes Compared
Here's exactly how our current fabrics compare — including pore sizes, construction type, and what each is best suited for.
| Fabric | Construction | Fiber | Pore size | Waterproof | Best for |
|---|---|---|---|---|---|
| AllergyCare™ 100% Cotton | Micro-weave | 100% cotton | 4.6 microns | No | Cotton sheet sleepers, hot sleepers, everyday use |
| AllergyCare™ Organic Cotton | Micro-weave | Certified organic cotton — non-dyed, non-treated, chemical-free | 5.3 microns | No | Chemical sensitivities, natural fiber preference |
| AllergyCare™ Stretch Knit | Laminated membrane | Polyester knit + 1-mil urethane membrane | Complete barrier | Yes | Children's beds, waterproof protection, bed bug protection |
All three fabrics provide complete, effective protection against dust mite allergens. The differences come down to comfort, feel, and whether you need waterproof protection — not whether one works and another doesn't.
Does a Smaller Pore Size Mean Better Protection?
This is the question we get most often — and the answer is: not necessarily, once you're below the threshold.
For dust mite allergens (up to 10 microns), any pore size under 10 microns provides complete protection. Going from 5.3 microns to 4.6 microns doesn't meaningfully improve your protection against dust mites — both stop them entirely.
Where pore size does make a difference is for smaller particles. Pet dander runs around 3 microns, and some mold spores are in the 2–5 micron range. If pet dander is a primary concern in addition to dust mites, a tighter pore size does offer an added margin of protection. But for the vast majority of dust mite allergy sufferers, all of our micro-weave fabrics are more than adequate.
Care Tips for Allergy Bedding
- Micro-weave covers (cotton and organic cotton): wash on a gentle cycle to protect the tight weave. Avoid chlorine bleach, which can break down fibers and widen pore sizes over time. Tumble dry low.
- Laminated covers (Stretch Knit): avoid high heat in the dryer — the urethane membrane is heat-bonded to the fabric and high temperatures can separate the bond. Line dry or use the lowest dryer setting. No chlorine bleach.
- How often: pillow covers monthly, mattress and box spring covers once or twice a year. Wash sheets and pillowcases weekly in hot water (130°F+).
The Bottom Line
Pore size tells you how tightly a micro-weave fabric is woven and how small a particle it can block. For dust mite allergy protection, you need a pore size under 10 microns — all of our AllergyCare™ micro-weave fabrics meet this standard comfortably. Laminated covers like Stretch Knit skip the pore size question entirely by using a complete membrane barrier.
The right fabric for you comes down to how you sleep, whether you need waterproof protection, and whether you have chemical sensitivities. If you're not sure, we've been helping people make this decision since 1989.
Call us at (800) 771-2246 — we're happy to walk you through it.
Shop all AllergyCare™ mattress covers →
→ Not sure which cover is right for you? Read our complete buying guide.
Medical Disclaimer: This content is for educational and informational purposes only and is not intended as medical advice. Always consult a qualified healthcare provider regarding allergies, asthma, or other medical conditions.