I promise to not make this into a dust mite blog. But as I mentioned previously, I’ve found it very difficult to find documentation of personal experiences of adults who are suddenly trying to deal with a dust mite allergy. There is a lot of information written by parents dealing with a child’s allergy, but not much about adults dealing with their own allergies. So I’m writing this partly to get it off my chest, and partly in hopes that it will be helpful to other people.

The primary method for dealing with a dust mite allergy is to encase each part of your bedding in an allergen barrier* — this means at a minimum you need to encase your pillows, your mattress, and your boxsprings. The encasing** completely covers each object — for example, the pillow encasing is like a regular pillowcase, but is a bit shorter and has a zipper on the open end to completely close it. You put your regular bedding (mattress pad, pillowcase, sheets) over the encasings. Everything that is not encased — blankets, sheets, pillowcases — must be washed every week (or even more often) in very hot water, in excess of 130 degrees (F), with bleach or borax (I prefer borax), both of which are effective in killing the mites. The encasings themselves get washed less frequently — I’ve seen recommendations that vary between once every two weeks to once every six months.

The purpose of the encasings is to create a barrier between a fibrous object (mattress, pillow, etc.) and your body. This barrier prevents allergic reactions in two ways: (a) it prevents the mites that are already in the object from escaping and causing an allergic reaction (imagine what happens when you flip over your pillow and put your head on it — a pillow without an encasing emits a cloud of dust mites, but a pillow with an encasing does not), and (b) it prevents new food (your skin cells) from moving into the object and hopefully reduces the size of the dust mite colony in the object. For most people, the first of these is most important — unless you buy new bedding, the existing dust mite colony in your mattress or pillow is probably large enough and has enough food that it probably cannot be significantly reduced.

Encasing seems a reasonable and sensible dust mite abatement strategy, but implementing it has been a challenge for me. There are dozens of companies that sell encasings under their own brand names, and there are no standardized terms for describing the fabrics they are made out of. Trying to compare products across companies is confusing and difficult. To make matters even worse, there is no standard method for grading or rating the degree of protection offered by each different fabric.

There are four basic types of fabrics used in encasings, ordered below from least expensive to most expensive:

(1) Vinyl. Vinyl comes in various gauges or thicknesses, from 4 to 6 (a higher gauge number means a thicker fabric). Vinyl used to be the only dust mite bedding option available, and it is still often used for children***. Vinyl provides a complete barrier to dust mites — the only place they can travel through it is at the zipper. However, it can be very uncomfortable, especially if you are a warm sleeper — it will make the bed clammy — and it rips easily. For adults, it’s used mainly to cover box springs because it’s cheap and completely impermeable — it can be put on once and never removed.

(2) SMS. SMS stands for soft/melt/spun. I don’t know why it’s called that. It’s an artificial fabric made from polypropylene that is strong and resists punctures. SMS is replacing vinyl for use on children’s beds, because it’s more comfortable than vinyl and it breathes better. I find that SMS has an unpleasant artificial feel, sort of like tyvek. Although it’s more breathable than vinyl, it will still feel clammy to a warm sleeper . For adults, it’s mostly used to cover box springs.

(3) Membrane fabrics. These are fabrics, often cotton or a cotton blend, that are laminated onto a membrane. The membrane is usually made of urethane. The membrane provides the allergy barrier, while the fabric is for comfort. Some companies advertise that their membranes are “breathable”, but I’m not sure I buy this. They are more comfortable than SMS or vinyl because they feel more like regular sheets, although the membrane can make them uncomfortable and clammy. If you aren’t a particularly warm sleeper, this might be a good option.

(4) Tight-weave fabrics. These are fabrics, usually cotton or a cotton blend but also found in polyester, that have extremely tight weaves, giving them very small pores (spaces between the threads). They do not have membranes because the pores are so small (usually in the 3-10 micron range) that dust mites (100 microns) and other allergens (cat dander is 6 microns) cannot move through it. These feel like stiff, thick sheets, and they breath like most other bedding, so they are the most comfortable option for most people.

The effectiveness of these fabrics as an allergen barrier is measured either by vacuuming various allergens through it (the only method for testing SMS or membrane fabrics, but also used with tight-weave fabrics) or by measuring the pore size (frequently the only method used for tight-weave fabrics). Vinyl is assumed to be a complete barrier and is rarely tested. For both measurement techniques, there is no standard way to conduct the test, so results of different manufacturers cannot necessarily be compared in any meaningful way.

After searching through the various websites and reading as much as I could, I decided the only sensible strategy for choosing a product was to choose a seller who seemed like they wanted to educate me rather than scare me, and who provided a lot of information about their fabrics. I realize this is less than ideal, but given how weedy this industry is, it’s the only way of picking a seller that made sense to me. I poked around the web for reviews, looked at blogs for cautionary tales, and ultimately decided to buy my encasings from AllergyGuardDirect. I am not affiliated with them in any way, but I am a satisfied customer. I can recommend their customer service and order fulfillment — they were helpful, answered my questions, and sent my order very fast.

I have an old-school king sized bed — it doesn’t have any kind of pillow top. It is 76×80x9 inches. Here’s what I ordered for it:
2 extra-long twin size 6-gauge vinyl covers, for my split-style box springs
1 king size 100% cotton tight-weave mattress cover
2 king size 100% cotton tight-weave pillow covers

With shipping, these 5 items cost about $140. The cotton tight-weave covers have pore sizes of 4.9 microns. All the products were of good quality and well made.

The vinyl covers smelled when they arrived, so I hung them over our banister for a few days to let them air out. If I had it to do over again, I would probably buy SMS or membrane covers for my boxsprings instead of vinyl, because the vinyl covers were hard to put on. But I was swayed by the promise of having a complete barrier on that part of the bed that requires little maintenance — I plan to wipe these down with a cloth occasionally, but I don’t plan to ever remove or wash them. If I had any chemical sensitivities, I would definitely have bought something other than vinyl. Ripping is a common problem with vinyl covers, and even though we were very careful when we put the vinyl covers on, one of them ripped — the hole was small, and I just covered it with duct tape, so it’s not much of an issue, but I probably would not buy vinyl again.

I am pleased with the mattress cover. It fits very well and was easy to put on. It’s also comfortable — I don’t notice it at all. I put my mattress pad over it and made the bed like normal.

I’m less pleased with the pillow covers. The pillow feels fine with it on, but I like my pillow to be cool, and I often flip it to the cool side when I wake up in the middle of the night. I find that my pillow is warmer with the cover on. It’s not hot, it’s just warmer than I’d like. I’ll probably get used to this, but for now it’s annoying me. I suspect I would have this problem with any pillow cover though, I don’t think it’s specific to this one.

So this first — and probably most important — stage of combating dust mites is finished. The cost wasn’t huge and the process was manageable, if confusing at times. I have one more major encasement to do — of my comforter. But I haven’t done that yet, and it’s problematic enough to warrant its own post. I’ve also massively de-cluttered the bedroom and instituted some necessary new laundry procedures. I’ll write about both of those activities over the next few weeks, as I accomplish them.


*These barriers have the added benefit of making your bedding impenetrable to bed bugs. With bed bugs on the rise across North America, and with my husband and I traveling and staying in hotels as much as we do, I do worry that one of us will come home with these unwelcome little hitch-hikers since even nice hotels are increasingly infested. I’m not providing any links, because the stories are gross — but you can google them up for yourself. I’m far more squeamish about bed bugs than dust mites, so I’m delighted to have this extra protection on my bed.

**This word bothers me. Why are these things called encasings rather than casings? I have no idea, but encasing is the term used not only by marketers, but also by researchers, so it’s the term I’m using here. I just wanted to point out that I find it annoying!

***I feel bad for kids that have to sleep on vinyl. In fact, I’ve noticed that most companies that sell encasings consistently recommend their cheaper, less comfortable products for children. I can only assume this is because the products probably get replaced more often for kids (as they move from cribs to “big kid” beds) and because they may need waterproof barriers in addition to allergen barriers. But I still feel really bad for them!

Posted on April 21st, 2008 by Katxena