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The Straight Dope



An article in the February 18 Wall Street Journal says, "The average mattress will double its weight in ten years as a result of being filled with dust mites and their detritus." This sounds impossible. Is it true? Who figured this out, and how?

--Nicki, via the Internet

Jeepers. You know how at night, when everything is still, you hear this faint roaring sound? Some people say it's the blood rushing in your ears. Uh-uh. It's the dust mites, chewing on your sloughed-off skin.

I contacted the Wall Street Journal reporter who wrote the article in question ("Those Costly Weapons Against Dust Mites May Not Be Worth It"). She said she'd gotten this amazing-if-true-but-don't-bet-the-rent story from a source at Ohio State University who was quoted elsewhere in the article. I tried reaching Emmett Glass, described in the story as "an OSU research associate leading the university's ongoing Dust Mite Management Study." So far he's eluded my clutches, but one of his colleagues told me, "I did hear Paul Harvey say that a person sheds 40 pounds of skin scales in a lifetime." Not to cast aspersions on a fellow media luminary, but my feeling is: Paul Harvey quotes scientist = good; scientist quotes Paul Harvey = bad.

Next I got in touch with a bunch of bug, allergy, and dust-mite experts, some of whom had been quoted in the Wall Street Journal article. Unsurprisingly, all dismissed the idea that there were mounds of mites in mattresses. "It's nonsense," said mite authority Larry Arlian, professor of biological sciences, microbiology, and immunology at Wright State University. "I don't know where that originated. They're not that prolific."

Thomas Platts-Mills, professor of medicine and dust-mite guru at the University of Virginia, agreed. "I've heard that kind of stuff," he said. "I don't believe it. I'm sure there's an added weight, but I don't think anyone has ever actually measured it." He suggested that perhaps someone vacuumed up a sample of dust-mite-laden household crud and extrapolated from that to the total weight of a mattress. Extrapolation can be a funny thing. You'll remember the column I did extrapolating from the reproduction rate of houseflies, in which I concluded that if Joe Letter Writer hadn't swatted a bunch one day, they'd have reproduced ad infinitum and filled up all the space in the universe. So extrapolations are something you want to take with a grain of salt.

Why is this silly story about mattresses full of dust mites (various species of the subclass Acarus, to get technical) being bruited about all of a sudden? Because there's a buck in it. Some folks are allergic to dust mites (actually dust-mite feces), and it may make sense for them to buy filters, vacuum cleaners, and other gimmicks that promise to get rid of the little bastards. Most people aren't allergic, but what the heck, if the hucksters can scare the pants off you, maybe you'll buy all that stuff anyway. One commercial Web site ( claims that a double bed contains over two million dust mites, that "a six-year-old pillow can have a tenth of its weight consisting of old skin, mold, dead mites, and mite dung," etc. An OSU fact sheet ( backs up these claims, but the experts I spoke to doubted them. That same commercial site, run by a pest control company, also says:

"[A] man from Clondalkin, Co. Dublin [Ireland], was playing golf when he was unwittingly infected with Weil's disease by a rat that ran up his leg and urinated on him. Three weeks later he became severely jaundiced and died shortly after when his kidneys collapsed."

So let's not get overly concerned about mites.

Art accompanying story in printed newspaper (not available in this archive): illustration/Slug Signorino.

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