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House dust mites are not a problem in Colorado!!

By Whitney Cranshaw, Colorado State University Extension Entomologist

House dust mites, or more specifically their airborne feces, are a potentially serious allergen.

Their basic food source are skin flakes - dander - which make up ca 80% of household lint.

However, they can't feed or develop on "raw" dander. It must be defatted and partially digested by an Aspergillus fungus.

The growth of the fungus requires fairly high humidity to grow. Further, at humidities much below 70% the mites tend to lose more moisture than they can acquire, which ultimately is lethal. It is generally considered that 60% RH is the absolute minimum where dust mites can occur. Given relative humidities found in this state average ca 35% or so (and considerably lower in homes during winter) that pretty much eliminates this problem.

Dr. Nelson of National Jewish Hospital in Denver did a survey of house dust mites in Colorado several years ago. He found none, with one exception. The exception was an invalid, confined to bed with a humidifier running constantly next to the bed. He concluded that they are not a problem in the state.

Despite this, articles about house dust mites continue to periodically crop up in local newspaper stories. They also are sometimes used in advertisements to create concerns so that people will buy products. One example is companies that clean heating ducts and picture a big house dust mite in advertisements.

I can think of fewer places that would be more unfavorable for a house dust mite to live than in a Colorado heating duct.

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Date last revised: 01/05/2010