Getting rid of dust mites—worthwhile?

This week, Dr. Sydney Spiesel discusses whether to get rid of dust mites, how the flu migrates, and what the risks are when taking psychiatric medication while pregnant.

Asthma and dust mites

Question: Asthma, now the most common chronic disease among children, has been increasing in prevalence worldwide for more than 50 years. All doctors know the common allergens that trigger the condition and the formulas universally recommended by the experts to clear the air. Throw the cat out the window. (OK, folks, lighten up—not literally!) Banish smokers to the back porch. Rip out carpets and damp mop the bare floors. And get rid of pesky dust mites —tiny insectlike creatures found in pillows, comforters, mattresses, and carpets whose corpses and poop collect in house dust. So, does decreasing exposure to dust mites actually decrease the risk of asthma?

New study: A recent review puts together the results of 54 studies, conducted with about 3,000 patients allergic to dust mites, and raises serious questions about the value of the dust mite wars. In each of the studies, patients were randomly assigned to either use or not use one of the standard methods of dust mite riddance. Then they were compared, using a variety of standard tests, to determine whether their asthma improved.

Findings: None of the dust mite attacks made any difference in asthma symptoms. In short, these expert-recommended, often expensive methods didn't benefit patients.

Explanation: Why should that be? As the authors point out, it's implausible to think that completely removing an allergen wouldn't decrease the allergic symptoms it causes. So, most likely, the recommended methods don't remove the dust mites. In fact (as I've pointed out before), some old and forgotten research has shown that the methods we use to fight off dust mites sometimes cause them to be fruitful and multiply.

Conclusion: There's another lesson to be learned from this study. The new watchword of medicine is evidence-based—the idea that the treatments we prescribe should follow from solid scientific research. Yet these findings should give us pause as we confront recommendations, like the recent "U.S. Guidelines for the Diagnosis and Management of Asthma," which gives us an expert but wrong assurance that solid evidence supports their recommendations. Including dust mite abatement.

Watch Dr. Spiesel's new video segment from Slate V:

Solving the mystery of the migrating flu

Question: Recent research on the movement of influenza viruses around the world addresses a mystery: Where do new epidemic strains of influenza come from?