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House Dust: Think Dust Mites!

A few weeks ago, I blogged about some of the components of house dust.  This week, as promised, I will discuss the presence of house dust’s most famous contaminant: dust mites.  

Dust mites are microscopic arachnids, which means they are in the same family as spiders.  They do not bite like bed bugs, but they can trigger an allergic reaction.

In a 1 gram sample of house dust, it is not uncommon to find thousands of dust mites (Portnoy 2013). That’s a lot of dust mites!  These creatures are about 245 microns wide and 440 microns long, so about the size of a grain of sand.  They feed on dead human skin cells in the dust.  This is a plentiful food source since a human sheds about a million skin cells per day (Colloff 2009).  Environmentally, dust mites respond well to humidity, in fact, they thrive when the relative humidity is higher.

The allergen for dust mites actually comes from dust mite feces.  Since 27.5% of the population in the United States is allergic to dust mites, it may be helpful to know that while humidity levels might be below 60% in the middle of a room, they can be much higher under the covers (Arbes 2005).  To get some relief from the allergic effects of these critters, it is recommended to monitor humidity levels in the home and maintain them below 50% (Cunningham 1996).  Using encasements around pillows, mattresses, and box springs can reduce the number of allergens that can escape from these materials.  Also, washing bedding, curtains, and other fabrics regularly in hot water can help eliminate the microscopic arachnid.

If you are concerned about dust mites, IAQ consulting companies like ours offer a test that checks for dust mite allergen.  However, in many situations, cleaning and reducing humidity levels can provide some relief against the little pest.  

The next time you wake up in the morning and start rubbing your eyes think dust mite feces!

Sources

Arbes, S.J.; Gergen, P.I.; Elliot, L; Zeldin, D. Prevalences of Positive Skin Test Responses to 10 Common Allergens in the U.S. population: Results from the Third Nutrition Examination Survey. I Allergy Clin Imunol. 2005, 116, 377-383.

Colloff, M. Dust Mites, 1st Ed.; Springer Publishing: New York, 2009.  

Cunningham, M.I. Controlling Dust Mites Psychrometrically – A Review for Building Scientist and Engineers. Indoor Air. 1996, 6, 249-258.

Portnoy, J., Miller, J. D., Williams, P. B., Chew, G. L., Miller, J. D., Zaitoun, F., … Wallace, D. (2013). Environmental assessment and exposure control of dust mites: a practice parameter. Annals of Allergy, Asthma & Immunology : Official Publication of the American College of Allergy, Asthma, & Immunology, 111(6), 465–507. http://doi.org/10.1016/j.anai.2013.09.018

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