Pillow and Mattress Encasings
There is much confusion about the different types of allergen-proof pillow and mattress encasings on the market today. These encasings vary widely both in the quality and type of their fabric, and in the quality of their sewing construction.
There are four basic types of materials used to manufacture allergen-barrier encasings: vinyl, laminates, woven microfiber fabric, and non-woven microfiber fabric.
Vinyl encasings are the oldest type, and the easiest to understand. They are inexpensive, effective…and uncomfortable. These plastic encasings are probably the first things that come to mind when most people think of an encasing. They are stiff, noisy and sweaty. As a result, many individuals remove them after a day or two. They are suitable, however, as an inexpensive cover for a box spring, where one is not sleeping on the plastic directly. The vinyl should be of sufficient thickness as to not tear easily.
Laminate encasings were the next generation of encasings developed. These are now used less often than previously (since the advent of microfiber encasings), but have recently been available at retailers such as Bed, Bath and Beyond, as well as from many allergy supply companies. They are made by laminating (fusing) a plastic-type membrane—now usually a polyurethane—to a fabric. The membrane side is against the pillow or mattress, and the fabric side is exposed, beneath the bed linens. The person is therefore not sleeping on the plastic directly, and these are therefore more comfortable than vinyl. Laminates do have several problems, however, that have made them somewhat out of date.
The first problem with laminates is that, although less rigid than vinyl, they are somewhat stiff. This is especially noticeable on the pillow. Second, like vinyl, they block the passage of air. Although some laminates have been advertised as being "breathable", this refers only to the fact that in the better quality laminates a minute amount of water vapor can pass through the membrane. Although this represents an advance over vinyl, the fact is that no laminate is truly breathable; that is, none of them allow the passage of air. Once an encasing of this type is zipped closed around a pillow, the pillow becomes like a balloon, with air trapped in the encasing. And if you force the air out by pressing on the pillow, the air--and dust along with it--escapes through the zipper.
The third problem with laminate encasings is that they often de-laminate. On other words, with repeated washing and drying the urethane membrane separates from the fabric onto which it had been coated, making the encasing unusable.
Woven Microfiber Encasings
Woven Microfiber encasings are the newest type of allergen-barrier encasing. They are constructed from microfiber fabrics: new high-tech fabrics made of fibers so thin and yarns so tightly woven that there is no space between the weave of the yarns large enough to allow the passage of allergen molecules. Since the microfiber fabric is itself acting as a filter that prevents allergen escape, encasings made from a true microfiber do not need the urethane membrane. Without the membrane they are truly breathable, that is, both air and water vapor can pass freely through the fabric, even though allergen cannot. They are therefore extremely comfortable, actually imperceptible in use. This is the state-of-the-art in allergen-proof encasings.
The problem is that not all microfibers are created equal. In fact, most of the so-called microfiber encasings on the market are not true microfibers at all, according to textile industry standards. Microscope photos taken at 80 power magnification reveal that many of the competitive products are much less tightly woven than Mission: Allergy barrier fabric. The areas of light coming through the fabric indicate pores. In many cases these pores are more than large enough to allow the passage of allergens. (Note: An interesting way of demonstrating the extraordinary tightness of Mission: Allergy microfiber barrier fabric is to simply put a few drops of water on it, and see the water bead up without penetrating.)
Studies done at the University of Virginia have shown that a microfiber fabric must have a pore size of no more than 6 microns to block all allergen. Mission: Allergy Premium barrier fabric has a mean pore size of slightly over 2 microns. Mission: Allergy Barrier II encasings have a mean pore size of 6 microns. Many encasings on the market have pore sizes of 10 microns or more. Unlike many competitive encasings, Mission: Allergy barrier fabrics block all allergens, not only mite allergens but also the smaller animal dander allergens. (This is important when a patient removes a pet from the bedroom, and the encasing must prevent the escape of previously accumulated allergen from the mattress.) Yet these super tight fabrics are the most comfortable on the market, literally as soft as silk, and cost no more than lesser quality encasings.
Non-Woven Microfiber Encasings
Non-woven Microfiber encasings cannot be recommended.
Unlike fabrics woven on a loom, non-woven fabrics are made by gluing and heat-sealing short pieces of yarn to each other to form a mass.
This type of inexpensive encasing, somewhat similar in appearance to a paper towel and recognized by an embossed pattern on its surface, is sold in many "big box" stores.
But recent studies have shown that dust mites can actually colonize them, and that dust allergen accumulates in the depth of their surface (see video).
Sewing construction is a final variable that must be taken into account. Poor sewing construction of some encasings results in gaps of a centimeter or more at the ends of the zipper, providing an opening for the escape of allergen. Higher quality encasings lack such defects. Other desirable features include bound seams to prevent the possible escape of the allergen through the seam stitching, and an interior zipper flap of barrier fabric that falls into place beneath the zipper, preventing the escape of allergen through the zipper webbing. Finally, extra long zippers (50% of the encasing's circumference) make placement of the encasing on a mattress much easier than when the zipper only extends one width of the mattress.
Not all encasings are equal!
It is of course up to the individual to decide what they want to buy and what they are willing to spend.
But if the above differences are understood, one will be in a position to make an informed decision.
Particularly with items related to health, it is better to obtain the proper quality at the onset, and not have to replace the items in a short amount of time.