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According to a new study published in the Textile Research Journal 2009, tightly woven fabrics with a thread count above 246 and a pore size between 2 and 10 microns, blocked more than 99% of dust mite allergens and prevented penetration of 100% of dust mites.
The study, Anti-mite Covers: Potential Criteria for Materials Used Against Dust Mites, published by:Vanna Mahakittikun, Prapakorn Ninsanit,and Teerapong Wangapai - Department of Parasitology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand and John Joseph Boitano - Stratford, Connecticut, USA and Chulaluk Komoltri - Clinical Epidemiology Unit, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand,tested 53 mite proof covers claiming to be anti-mite from 10 different countries. The samples comprised tightly-woven ( over 265 thread count ), film/membrane coated woven, acaricidal-coated woven, non-woven, membrane-coated non woven, acaricidal ( ceramite,chitosan )-coated non-woven, plastic, and woven/non-woven combo fabrics. Three regular, cotton bed sheets ( 180 thread count ) were also tested and used as a comparison.
Keep in mind that these products tested were all claiming to be anti-mite covers specifically marketed to prevent dust mites and their associated allergens from infiltrating consumer bedding.
They concluded that while plastic and film/membrane fabrics performed well, because of the air permeability restrictions of these fabrics, tightly woven fabrics with an air permeability factor of between 2 and 6cm3/s/cm2 were the only fabrics to fulfill the requirements of performance and comfort.As well, tightly woven fabrics treated with acaricides fared no better than ones without acaricides. Fully 41% of the fabrics tested failed to meet the basic requirements, these included loosely woven fabrics treated with acaricides and non-woven fabrics.
The study also points out that it is not unreasonable to assume that repetitive launderings of all the various covers, other than plastic, would substantially degrade the performance over time, according to a study they cite. But, other studies cited, suggest the structural integrity of tightly woven covers was not compromised.
Their conclusion: " "that plastic and tightly woven covers block mite penetration and prevent leakage of allergens while other types of covers fail. The minimum criteria suggested is a fabric with a pore size between 2 to 10 mair permeability should be greater than 2 and less than6cm3/s/cm2; and a thread count greater than 246/in2 " What does this mean to the average consumer ? Basically they are saying that any tightly woven cover of more than 246 threads per inch is sufficient to block dust mites and their allergens. Coatings and chemicals have no benefit over a tightly woven fabric, and while plastic blocks mites and allergens, it is not air permeable, so it will be uncomfortable Finally the consumer has a baseline from which to make their decision on what kind of protection they choose and how much to pay for it. No longer will you have to pay for fancy coatings, chemicals, and false claims. What you do need, is a well constructed, high quality fabric with a thread count of more than 250. Whether you choose 100% cotton or a poly/cotton blend or just polyester, becomes a choice based on comfort and whether or not you have a sensitivity to synthetic materials. Choosing a mattress encasement, cover or travel sheet, no longer rests on the smallest pore size because anymaterial under 10 microns will block 99% of dust mite allergens and all mites. What you must remember is that on top of your mattress cover or encasement, you will also use a sheet. Combining the two, given that both are at least 250 thread count, your protection will be excellent.
The other major factor other than the fabric's ability to block allergens, is the method of closure. Usually, when talking about encasements, the preferred method of closure is a zipper. The zipper should be able to stand up to repeat washings without rusting or breaking. The ends of the zipper should not have any voids or spaces, a well made encasement will have overlapping flaps to prevent escape or entry by any pests.
Washability, how will the cover stand up to repeat washings. What temperature can you use to wash and dry the encasement. Remember, according to the American Thoracic Society,hot water , above 140 celsius, will kill 100% of dust mites and bedbugs, 90% of dog dander and remove 96% of pollen.Lower the temperature just 36 degrees, to warm, means a significant drop in pest and allergen removal. Most cotton protectors cannot be washed in hot water and even fewer can go through a drying cycle on high, the shrinkage would be too great or the fabric would not hold up.
In short, thread count and washability and pore size, are the three primary factors in choosing a mattress encasement, cover, protector or travel sheet.
Disclaimer: All information on this site is provided for informational purposes only! By no means is any
information presented herein intended to substitute for the advice provided to you by any health care or other professional
or organization.
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